prelim bio - NOTES!
as with the thread posted before, ive got a bit of notes, um.. some pple didn recieve it when i emailed it to them, so im copying and pasting, and praying its gonna work
Revision for Year 11 Biology
Terrestrial and aquatic environments: Chapter 1
The environment of an organism is its surroundings- everything around it (both living and non-living).
An ecosystem is any environmental containing living organisms interacting with each other and with the non-living parts of that environment.
The habitat of an organism is the place where it lives. The organisms which are found living together in a particular place form a community. The study of the relationships living organisms have with each other and with their environment is called ecology.
Environments have abiotic and biotic features.
o Abiotic means not-living. Features include physical and chemical factors such as the temperature, rainfall, type of soil, and the salinity of the water.
o Biotic means living. Features include all the living organisms, how many types there are, their numbers, distribution and interactions.
Terrestrial environments are environments on land. Land covers about 35% of the Earths surface.
Organisms that live in water live in an aquatic environment. Aquatic environments may be freshwater ( still water such as lakes, ponds and swamps), or saltwater (e.g.: open seas, and saltwater lakes).
Terrestrial and aquatic environments have very different abiotic characteristics. These differences mean that, in order to survive, animal and plants living in an aquatic environment will be very different from animals and plants living in a terrestrial environment.
The distribution of species is all the places in which it is found. No species is spread evenly through an entire natural ecosystem.
The abundance of a species means HOW MANY members of the species live throughout the ecosystem. Abundance is not same throughout the area, and changed over time. A species will increase its abundance if the birth, or germination rate exceeds the death rate; if its resources are plentiful and there is not much predation or disease. Increases in the abundance of animals are caused by births, and immigrations, decreases are due to deaths, and emigrants.
All organisms have their own requirements for successful survival and maximum growth and development. The word: resources is often used in reference to factors affecting distribution and abundance of organisms. Resources are anything in an environment that organisms use. Resources are usually limited, organisms that need the same resource will be in competition.
Abiotic factors:
o amount of light
o amount of strength of wind and rainfall
o temperature: daily and seasonal variations
o effects of topography, altitude and depth
o strength of tides, currents and depth
o amount, salinity, pH and availability of water
o type and amount of substrate
o availability of space and shelter
o oxygen availability
Biotic factors
o Seasonal availability and abundance of food for animals
o Number of competitors
o Number of mates available
o Number of predators
o Number and variety of disease-causing organisms
A profile sketch is like a cross section.
A Plan sketch of the same area, shows us more information about the extent of the species. (also called an areal view).
Viscosity is a resistance force (it is greater in water, than it is in land)
Buoyancy is the amount of support experienced by an object. The buoyancy of water offers support to both animals and plants. While on land, animals and plants to do not experience much buoyancy from air.
Temperature variation- (the main source of heat is from the suns radiation), water heats up more slowly than air. Surface areas on land vary far more than in water.
The earths gravitational field (the pull of gravity) gives rise to pressure differences between the upper and lower layer in both air and water. Pressure in water increases rapidly with depth. Atmospheric pressure decreases with height above sea level and also fluctuates over time- may affect breathing by animals and flight.
Oxygen and carbon dioxide are important gases for living organisms.
o Gas availability in water depends on the temperature, and diffusion is slower.
o Gases are freely available in air.
OSMOTIC (the water moves in the direction of higher concentration)
Light falling on water may be scattered, reflected or absorbed. Light is received from the suns radiation. while light can pass freely through air.
All organisms have their own requirements for successful survival and maximum growth and development. Resources- anything in an environment that organisms use. Resources are usually limited, organisms that need the same resource will be in competition.
Plants need light and water for photosynthesis- the rate of growth depends on temperature and soil or water quality.
A group of similar organisms living in a given area at the same time is known as a population.
Scientists have developed sampling techniques to make estimates of the distribution and abundance of species.
The reason population estimates are made is because of the difficulty in describing in detail any large area. It would be impractical and time-consuming to count every living thing- it would also damage the environment!
A transect is a narrow strip that crosses the area being studied, from one side to another.
A quadrant is a small area that is being selected to represent the larger area being studied.
Plant abundance- percentage cover
Animal abundance :
(method called capture-recapture)
When the number of organisms in a population increase dramatically over a short period of time, we say that there has been a population expulsion.
A food chain represents the flow of energy from one living thing to another.
Food chains begin with plants. The first consumer is called a primary consumer it is then eaten by the secondary consumer, which then may be eaten by the tertiary consumer: and so on.
When you draw a food chain, start with a producer, and point the arrows in the direction that the energy and matter flow.
Scavengers are consumers that eat dead animals. Decomposers are organisms such as fungi and bacteria that cause decay. Decomposers have an important role to play: they make the materials produced by decomposition available to plants. It is then recycled in food chains.
In most ecosystems there is more than one primary consumer, and animals often eat more than one thing. To show the complex feeding interactions in an ecosystem, we use a food web.
Biomass is the amount of living material in an organism or group of organisms at any one time.
All living things ultimately depend on the process of photosynthesis.
CARBON DIXODE +WATER (light energy + chlorophyll) sugar + oxygen
(symbol equation)
Photosynthesis is the process by which plant cells capture energy from sunlight and use it to combine carbon dioxide and water to make sugar and oxygen. It takes place in the chloroplasts of the green parts of the plants.
Chloroplasts are organelles in plant cells. Light energy comes from the sun, which is the light energy source.
All living things ultimately depend on the process of photosynthesis.
Word Equation: Carbon Dioxide + Water (light energy + chlorophyll) sugar + oxygen.
SYMBOL EQUATION
Photosynthesis takes place in the chloroplasts of the green parts of the plants.
Chloroplasts are organelles (structures within a cell) in plant cells. Light energy comes from the son, which is the light energy source.
Glucose + Oxygen Carbon Dioxide + Water + Energy (this is the respiration equation)
This process is carried out in all living cells.
Respiration is carried out in the organelle called the mitochondrion (plural=mitochondria)
Respiration involves a series of 50 different reactions= and each one is catalysed by a different enzyme.
Energy is released slowly in small amounts
THERE ARE 2 STAGES OF RESPIRATION
Stage 1 occurs in the cytoplasm.
The splitting of 6 carbon sugar molecules ( ) into two 3 carbon molecules, called pyruvate, and the making of two molecules of ATP
Stage 2 occurs in the mitochondria
It uses oxygen (which we call aerobic). The pyruvate breaks down into oxygen and water and 36 ATP molecules form.
60% of the energy is lost as heat, and 40% of the energy is glucose converted to ATP.
How is the energy from respiration used?
o Synthesis of complex molecules such as proteins, lipids, carbohydrates and nucleic acids.
o Growth involving the division, elongation and differentiation of cells.
o Repair and maintenance of damaged or old cells
o Active transport of materials across cell membranes
o Functioning of special cells that need extra energy, such as nerves, muscles, liver and kidney in mammals.
o Transport of materials within organisms, such as the phloem of plants and circulatory system of animals.
We (as humans) have disturbed many natural ecosystems to meet our own needs. However, we are quickly learning that god management of these systems is essential if they are to function efficiently. In ecosystems there is a flow of energy and materials, energy is a one-way flow, and materials are recycled.
Humans have a great impact on ecosystems. We deliberately change our environment to suit our own needs. In doing so, we bring about rapid alterations and widespread change. Our effect is often destructive to the original environment and its other inhabitants.
The removal of vegetation for farms, towns, roads and other human uses has lead to soil erosion. Crops eat up soil nutrients. Run-off from the use of fertilizers causes pollution in waterways.
Environmental pests and weeds can be controlled by physical, chemical or biological means.
PHYSICAL- control includes shooting animals and cutting down or digging out plants.
CHEMICAL- control includes use of poison baits and insecticides for animals and herbicides for plants.
BIOLOGICAL- control involves the introduction of a predator or parasite.
Pollution is the spoiling or poising of the environment though human activity.
There is a need to balance the human activities and needs in ecosystems to conserve, maintain and protect the quality of the environment.
o Many global organizations and international agreements address the quality of the environment. Greenpeace, The World Wide Fund for Nature.
o The convention on International Trade in Endangered Species of Wild Flora and Fauna (CITIES) lists those plants and animals that are not permitted for international trade.
o The national Heritage Trust (Australia now has 13 World heritage Areas)
o The World Heritage List notes those areas in the world of high importance to conserve for the future.
Role of teeth:
The action of teeth (incisors and molars) breaks down food to increase the SA:V ration for the digestive chemicals to process.
Animal cells, which are heterotrophic, must obtain food from the external environment. The digestive system is the means by which external cells are taken into the organism and broken down (digested).
The process of digestion involves the mechanical (teeth) and the chemical (saliva, digestive juices) in the breakdown of food. Complex molecules are broken down into simple molecules by specialised proteins known as enzymes.
There are three types of digestive enzymes:
Amylases- act on carbohydrates
Proteases- act on proteins
Lipases- act on lipids
Food is broken up by teeth and mixed with saliva for lubrication before swallowed. The digestion of carbohydrates may also begin in the mouth.
Relationship between herbivore and carnivore, with respect to: their chemical composition of their diet, and the functions of the structures involved.
A Carnivores digestive system is less complex and proteins can be more easily digested in the stomach.
Herbivores: need a more complex digestive system because plant material contains cellulose fibres which are harder to digest.
Structure/ Physiology Carnivore (Dog) Herbivore (Cow)
Teeth Have large canines to tear and rip meat Large flat double teeth (molars) to grind plant food
Length of time food spends in stomach (digestion) Approx 1 hour, this is a short time Approx 1 day, this is a long time
Small intestine Spread out, long, it has a large SA for absorption Long and compacted. It also has a large SA for absorption
Caecum Small; attached to side Large; because bacterial fermentation of plant material breaks down cellulose fibres. Regurgitation occurs
Faeces (water and salts that are eliminated from the digestive system) Small, dry Fibrous Faeces- more dry and large
Large Intestine Short, straight, flat Long, coiled, thinner
A herbivores diet is largely composed of cellulose. No vertebrates produce digestive fluids that can digest cellulose. Instead, micro-organisms in the colon convert cellulose into sugars. This process is extremely slow. The long colon provides increased SA for the action of microbes on the cellulose. They have complicated stomachs that consist of 4 chambers.
The Nectar feeder
The Honey possum feeds on pollen, nectar and insects. It has slender long incisor teeth and flanges on its upper and lower lips that form a channel through which a very long tongue is retracted. Nectar and pollen are scraped off the tongue as it is retracted. The digestive system is special in that a diverticulum branches off the stomach and severs as a storage container for nectar. Pollen does not appear o pass into the diverticulum but appears to be digested in the small intestine. There is no caecum.
Explain the roles of respiratory, circulatory and excretory systems:
Respiration:
Living cells need oxygen for respiration and carbon dioxide is produced as a result of respiration. When it dissolves in water, it forms carbonic acid.
We have respiratory systems to exchange gases with the external environment, and to enable cellular respiration to occur.
Circulatory:
Multicellular animals need to transport or circulate materials around their bodies to supply cells with nutrients and remove wastes (so that all cell requirements are met). The flow of materials is usually maintained by a pumping system. They can be open, or closed.
Open Circulatory Systems: (invertebrates such as arthropods and molluscs)
In insects this involves the circulation of body fluid, known as HAEMOLYMPH, (this is not blood) around the body by a simple pumping system consisting of one or more tubular hearts. Haemolymph bathes the tissues and accumulates in spaces within the insect. Any vessels that assist the transport of the fluid are open at each end. Fluid is sucked into tubular hearts through small holes. It is then pumped forwards to the front end of the insect and flows slowly backwards through the spaces surrounding the various organs. Pressure in an open system is low, so the body fluid circulates slowly.
Open Circulatory systems suit the needs of smaller animals. In insects, they do not have to transport respiratory gases, but only distribute and collect food and wastes, and sometimes store them temporarily.
[Distribution to cells/tissues: fluid flows through the tissues spaces]
Closed Circulatory Systems: (large active animals such as vertebrates and squids)
In humans, the closed circulatory system consists of a muscular pump (the heart) that forces a fluid (blood) through a closed system of tubes (blood vessels), which carry materials rapidly throughout the body. No cell in the body is very far from a blood vessel.
Distribution to cells/tissues: fluid from the blood becomes part of the body fluid which bathes all the cells.
Vessels (veins): are closed, come into and out of the heart (arteries).
Pressure: high, fast blood pumping.
Closed respiratory systems meed the need of large, active animals. They provide nutrients and oxygen to cells and carry away wastes and carbon dioxide. However, they use more energy to provide the faster service required.
Excretory:
The metabolic processes that occur in the cells of living organisms constantly produce wastes that must be removed. If not, cells would be poisoned. The main excretory products of cells are Carbon Dioxide (produced in respiration), and nitrogen (containing nitrogenous wastes produced from the breakdown of proteins and nucleic acids).
Identify the features of respiratory surfaces of multicellular animals including fish, insects, mammals and amphibians (frog)
FISH: Eg: Exposed gills hammerhead shark) Covered Gills (mullet, goldfish etc)
Respiratory surfaces are gills over which water flows. Some fish have exposed gills (eg; sharks) and others have gills covered by an operculum (eg: bony fish).
Gills are usually finely divided and the incoming water flows over a large surface area at the one time. Water flows over the gills, and then the gills open up and absorb oxygen. The blood vessels are in contact with gills.
INSECTS: Eg: Grasshoppers
Have a system of branching tubes called tracheae within their body. The tracheae is open to the external environment through pores or spirals along the abdomen. The trachea branch throughout the tissues of the insect, brining air directly to the cells. Because the insects are usually quite small, the SA of the trachea is sufficient to supply all the body cells.
MAMMALS: Eg: Humans, Kangaroo, Monkeys
In mammals, gases are exchanged in the lungs. These surfaces are protected from desiccation by being inside the bodys water-proof covering. The surface area of contact between the blood and air is increased by the convolution of the lungs into lobes, by the branching of the bronchioles into smaller tubules, and by the division of the tubules into clusters of tiny air sacs called alveoli. There is plentiful blood supply to transport gases to and from the lungs.
AMPHIBIANS: Eg: Green and Golden Bell Frog, Green Tree Frog
Have two respiratory surfaces: Lungs and Skin.
There is a very well developed blood supply to the skin. Oxygen from the air diffuses into the moist skin and is transported by the blood, to the heart from where it is sent directly to the body.
The lungs are simpler structures with a smaller surface area than those of mammals. This is why they need the skin as a respiratory surface as well.
Relationship between the requirements of cells and the need for transport systems in multicellular organisms
The more cells you have in an organism, the more transport systems that enable substances to be moved to and from the internal body cells, are needed.
Transport systems are needed by multicellular organisms to ensure that all the requirements of their cells are met.
Every cell must receive oxygen and get rid of its wastes.
Multicellular animals need to transport or circulate materials around their bodies to supply cells with nutrients, and to remove wastes.
The flow of materials is usually maintained by a pumping system. Circulatory systems may be open or closed.
1. Identify mitosis as a process of nuclear division and explain its role
2. Identify the stages of mitosis in plants, insects and mammals
3. Explain the need for cytokinesis in cell division
4. Identify that the nuclei, mitochondria and chloroplasts contain DNA
DNA is also found in mitochondria, and chloroplasts. These organelles can also replicate within a cell.
Mitosis is a type of cell division that results in the production of cells which are identical to the original cell.
The stages of mitosis:
PROPHASE (early stage): Each chromosome is visible as two identical, joined strands, called chromatids. The nuclear membrane breaks down and disappears by late prophase.
METAPHASE (middle stage): A tapered system of microtubules stretches across the cell, forming a spindle. The chromosomes line up at the centre of the cell, attached to the spindle fibres at the point known as the centromere. The chromosomes separate (In animals, the centriole is involved in spindle formation. Centrioles are absent in plants, so the spindle attaches itself to the cell wall).
ANAPHASE (toward the end stage) The Chromatids, now referred to as single-stranded chromosomes, more toward opposite poles, carried on spindle fibres.
TELOPHASE (end phase) The spindle disappears. New nuclear membranes form around the two sets of chromosomes.
The need for cytokinesis (the division of the cytoplasm- a distinction from the division of the nucleus)
Division of the cytoplasm occurs immediately after mitosis. This is necessary to ensure that the chromosome number in each cell remains constant. The chromosome number doubles in mitosis and one cell now contains two sets of chromosomes.
IN ANIMAL CELLS, THE CYTOPLASM CONSTRICTS AT THE CENTRE IN A PROCESS CALLED CLEAVAGE. A ring of microfilaments forms in the centre of the cell. As they constrict, the cell beings to cleave into two. The cell surfaces show very active movement as they separate. In plant cells, a dividing plate (the cell plate) forms across the centre of the cell, separating the two new cells (daughter cells). A new cell wall is built from this plate.
Identify the sites of mitosis in plants, animals and mammals
MAMMALS: mitosis occurs in the skin, replacing the cells that continually flake off, and causing hair/fur and nails/claws to grow. New blood cells are made every day in the bloody marrow, and in cells lining the digestive system is constantly being replaced.
INSECTS: Most insects have immature forms known as larvae. When larvae hatch from the egg, they grow and increase in size, but this is a result of cell enlargement, not cell division. In the pupal for, the larval cells break down, ad previously inactive groups of cells known as imaginal discs start to divide. They grow in both size and number to from the adult insect or imago.
PLANTS: In mature plants, mitosis occurs in the tips of roots and stems, causing an increase in length. Mitosis in special cells in the stem results in an increase in its width.
Plants continue to grow throughout their life from cells capable of mitosis known as meristematic cells.
Scientists estimate that the universe is 10-20 billion years old, and arose as a big bang, which is still expanding in the universe. Some matter in the universe condensed into solar systems called galaxies.
The early earth which originated 4.5 billion years ago, was very different and no oxygen was present. The atmosphere consisted of hydrogen, carbon monoxide, methane and ammonia.
Organic chemicals appear to have originated 4 billion years ago.
ORGANIC MOLECULES & MEMBRANES
Early organic molecules could have formed microspheres to separate living chemicals from the environment. The organic molecules react with each other making this the first metabolism. They needed to be separated from their surroundings in order to metabolize effectively so the first membranes were formed, with the lipids and proteins joining together. This lead to the first primitive cells.
PROCRAYOTIC HETROTROPHS & PROCRAYOTIC AUTOTROPHS
Prokaryotes are believed to be the first cell type. Hetrotrophs use chemicals (Carbon, and Water, from outside to gain energy and synthesis their molecules. These would use up all the biological molecules in their environment and this set up selective pressure for cells to make their own molecules from simple sources- these would be more likely to survive. These are the first autotrophs, and without them, life would have come to an end. Hetrotrophs and prokaryotes then relied on autrotrophs.
Prokaryotes consist of a cell wall, and a cell membrane enclosing cytoplasm, containing organic chemicals.
Once eukaryotic cells have evolved, they proceeded to diversity into colonies, then mulitcellular organisms;
Eventually producing plants, animals and fungi.
Success of Prokaryotes- several factors contribute to this
1. Fast rate of reproduction
2. varied metabolism
3. ability to form spores and remain dominant for years
4. use of nutrients which are inaccessible to other organism (i.e.- nitrogen)
A fossil is the remains or record of an organism that lived in the past. They provide a record over time of how things have been evolving on earth. Conditions must be right at the time of burial for an organism to become fossilised.
Fossils can tell us many things about life during the past. Using them, we can find out about species that lived long ago, and the environment in which they lived in. We can also date rocks by comparing them with fossils found at other sites.
a) Animal Fossil- Trilobite, found at kangaroo island, South Australia.
Trilobites appeared on the earth 546- 250 millions of years ago; during the Lower Cambrian age. During the Cambrian period, the climate was tropical and all life was in water. The earliest Trilobites were bottom-dwelling, crawling scavengers and mud processors. They were the most abundant and diverse species at the time, and were important animals in the oceans for over 200 million years. They lived mainly in clear, shallow seas that were teemed with life. There were over ten thousand different species of the Trilobite. Fossils of the closest relatives of Australian trilobites have been found in Malaysia, Thailand, Burma, China and the Mountains of Tibet. This suggests that these countries were once joined together.
The Trilobites name came from the division of their body. There are three divisions (central axis lobe, and two lateral lobes). The physical structure of the Trilobite is divided into three sections; the cephalon (the head), thorax and the pygidium (the tail).
They were one of the first animals to develop a hard outer covering over its body, and so fossil remains are found all over the world. Also, because of their outer covering, they were able to survive in a number of different environments.
The majority of the Trilobites were sightless. They had either single lens eyes, or compound eyes composed of a large number of discrete visual bodies. Overtime, however, they developed eyes that could see very well in dim light at the bottom of the sea.
The optimum time for the Trilobite was reached during the Late Cambrian. Then afterwards, their numbers began to decline perhaps in response to predation from cephalopods and fishes, and possibly drying of the land. They were extinct near the close of the Paleozoic.
It can be deduced that the land during the Cambrian age was fairly moist, as the Trilobites lived in watery environments. It can also be thought that towards the Paleozoic era, the land began to dry, as the trilobites became extinct.
Trilobites do not exist today and this tells us that the environment long ago is a lot different than the environment today.
b) Plant Fossil- Ferns, (Pterospids) found at South Gippsland and the Otway Ranges in Victoria.
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Ferns (Pterospids) were widespread in the Carboniferous age (more precisely, the Pennsylvanian time) and became extinct in towards the end of the Tertiary period. It was known as the Age of Ferns as they were both abundant and diverse, and were also a dominant part of the vegetation at that time. The were among the oldest kinds of plants that lived on land.
They were common in coal swamps. They could live in a diverse range of environments; however the spores could only germinate in very damp conditions. So, it can be deduced that where ferns were found, water must have been present.
They ranged in size from the small, delicate plants found in temperate climes to the big-leafed tree ferns of the tropics. Ferns have a well-developed vascular system; clear differentiation into roots, stems and leaves.
Today however, a number of different types of ferns exist (the ferns that existed during the Carboniferous age are now extinct). [Today, fern is a common name for any of a division of cryptogamous (spore-producing) plants.] This also tells us, that the environment long ago is different from that of today.
Oparin
In 1924, Russian biochemist Oparin proposed that life had arisen from simpler molecules on the lifeless earth under much different atmospheric conditions than those that exist today; over a long time.
Haldane
In 1929, English biologist Haldane published a paper in which he proposed that ultraviolet light (from the sun), when acted upon the Earths primitive atmosphere, produced a vast array of organic compounds (ammonia, hydrogen, methane with water). These compounds accumulated in oceans until they had the consistency of a hot dilute soup.
Haldane and Oparin believed that life could have evolved in the conditions of the early earth.
In conclusion; Oparin and Haldane made a hypothesis about the origin of life, and Urey and Miller provided the evidence by conducting an experiment as outlined below.
Urey and Miller
In 1953, Urey and Miller performed their famous experiment whilst working at the University of Chicago. They wanted to test if it was possible for organic molecules to have formed in a reducing and energy-rich environment similar to the early earth . Many say that they proved life can come from chemicals. Their work tied in with Albert Einsteins work and Charles Darwins theory of evolution. They started with the components of the Earths primitive atmosphere (methane, ammonia, hydrogen and water) and placed these in a five litre boiling flask, an in the apparatus shown below. They also ran a continuous electric current through the system, to simulate lightening storms that were believed to be common in the primordial earth. Boiling water produced steam, which helped to circulate the gasses through the system.
They left this apparatus for one week, then analysed the water containing organic compounds.
Products of the Miller and Urey Experiment:
Tar 85%
Carboxlic acids not important to life 13.0%
Glycine 1.05%
Alanine 0.85%
Glutamic Acid Trace
Aspartic Acid Trace
Amino acids are more commonly known as building blocks, as they are required in the manufacture of protein, which are essential for growth and repair. There are fifty known amino acids, four of these fifty occurred in this experiment (Glycine, Alanine, Glutamic acid and Aspartic acid). So, a number of substances related to life were synthesized as a result of the above apparatus. It is evident from the results that organic molecules were produced in the simulated conditions.
Miller and Urey concluded that life can come from inorganic substances.
The importance of their experiment in showing the nature and practice of science is apparent. They had proposed a model and through experimentation, it was demonstrated that the model could have correct. Miller and Ureys experiment was repeated a number of times by various scientists, and each time they changed a variable, no amino acids resulted.
Their contribution to hypothesis about the origin of life helped many scientists in future decades. They provided the experiment (and inturn support) for Haldane and Oparins theories about how the first organic molecules could have formed.
In sexual reproduction, sex cells must be transferred from where they are made to where they can join.
There are two types of fertilisation.
a) External Fertilisation
In this method, the egg and sperm unite outside the bodies of the parents. This is usually the case with most aquatic organisms such as; sea urchins, starfish, clams, mussels, frogs, corals and many fish.
The gametes are released into an ocean or pond, where embryos begin to develop. The meeting of the egg and sperm is left to chance as swift water currents, temperature changes and predators can prevent fertilisation. As a result, millions of sperm and egg are produced. This way, even if a fraction of the sperm and egg meet, several offspring will still result.
Example of External Fertilisation: Frogs
Eggs contain all the food and protection needed for the growth of a new animal. A simple diagram of an egg is outlined and explained below.
However, not all external-reproducing organisms have eggs like this. As shown above, the eggs of fish are light and transparent due to the risk of being eaten. Reptiles and birds produce shelled eggs to try to overcome the difficulties and threats on land. It also seems that many eggs that develop on land, have developed their own natural sunscreens, as a protection from the sun.
b) Internal Fertilisation
Organisms that are on land, face the problem of sex cells and the developing zygote drying out. So, in most multicellular land organisms, the female sex cell is fertilised inside the female organism. This occurs within the females body. This type of fertilisation is more common with terrestrial organisms such as; mammals, reptiles, birds as well as some invertebrates including snails, worms and insects. The male typically has a penis or other structure that can effectively deliver sperm into the females reproductive tract.
However, in internal fertilisation, the sperm and egg are always protected in both the males and females bodies, and are placed in close contact during mating. Because of this, few sperm and egg are produced.
Example: Internal Fertilisation- Human (Mammals)
Pre-Labor
Placenta increases its surface area, to
increase flow of nutrients,
and disposal of wastes.
Blood supply to uterus increases, to supply
nutrients to the embryo. Breast size increases, carrying milk for the baby.
During Labor:
Pelvic joints become loose to allow a passageway for the foetus.
Uterine muscles begin to contract at regular intervals. As the time between contractions becomes shorter, the contractions become longer and more intense
Forceful uterine contractions push the foetus from the uterus, through the birth canal
The foetus head moulds- to allow for an easier delivery.
Post Labor:
After birth, the placenta separates from the uterine wall and is expelled. This is to prevent bleeding.
In addition, the baby is born with a sucking ability, so when he/she sucks on the mothers breast it stimulates the brain, which releases hormones and inturn stimulates the mothers chest to produce milk. Mammals, (especially humans) also tend to take great care of their young after they are born.
SPEECH ON FOSSILS:
For my plant fossil I picked the ferns, and these can be found along the east coast of Australia. These were found in South Gippsland and the Otway Ranges in Victoria. They were widespread in the Carboniferous age, as this was known as the age of ferns, as they were both abundant and diverse, and were also a dominant part of the vegetation at that time. They became extinct towards the end of the tertiary period.
They were very common on coal swamps. They could live in a diverse range of environments, however they could only reproduce in watery conditions. Therefore, it can be deduced that were these plants were found, water must have been present.
They ranged in size from the small delicate plants, to the big leaded tree ferns of the tropics.
Today, these ferns are extinct, and the word fern is now a common name for any division for spore-reproducing plants. This tells us, as with the trilobite (as they are both extinct) that the environment and species that live today are very different from those that lived long ago.
as with the thread posted before, ive got a bit of notes, um.. some pple didn recieve it when i emailed it to them, so im copying and pasting, and praying its gonna work
Revision for Year 11 Biology
Terrestrial and aquatic environments: Chapter 1
The environment of an organism is its surroundings- everything around it (both living and non-living).
An ecosystem is any environmental containing living organisms interacting with each other and with the non-living parts of that environment.
The habitat of an organism is the place where it lives. The organisms which are found living together in a particular place form a community. The study of the relationships living organisms have with each other and with their environment is called ecology.
Environments have abiotic and biotic features.
o Abiotic means not-living. Features include physical and chemical factors such as the temperature, rainfall, type of soil, and the salinity of the water.
o Biotic means living. Features include all the living organisms, how many types there are, their numbers, distribution and interactions.
Terrestrial environments are environments on land. Land covers about 35% of the Earths surface.
Organisms that live in water live in an aquatic environment. Aquatic environments may be freshwater ( still water such as lakes, ponds and swamps), or saltwater (e.g.: open seas, and saltwater lakes).
Terrestrial and aquatic environments have very different abiotic characteristics. These differences mean that, in order to survive, animal and plants living in an aquatic environment will be very different from animals and plants living in a terrestrial environment.
The distribution of species is all the places in which it is found. No species is spread evenly through an entire natural ecosystem.
The abundance of a species means HOW MANY members of the species live throughout the ecosystem. Abundance is not same throughout the area, and changed over time. A species will increase its abundance if the birth, or germination rate exceeds the death rate; if its resources are plentiful and there is not much predation or disease. Increases in the abundance of animals are caused by births, and immigrations, decreases are due to deaths, and emigrants.
All organisms have their own requirements for successful survival and maximum growth and development. The word: resources is often used in reference to factors affecting distribution and abundance of organisms. Resources are anything in an environment that organisms use. Resources are usually limited, organisms that need the same resource will be in competition.
Abiotic factors:
o amount of light
o amount of strength of wind and rainfall
o temperature: daily and seasonal variations
o effects of topography, altitude and depth
o strength of tides, currents and depth
o amount, salinity, pH and availability of water
o type and amount of substrate
o availability of space and shelter
o oxygen availability
Biotic factors
o Seasonal availability and abundance of food for animals
o Number of competitors
o Number of mates available
o Number of predators
o Number and variety of disease-causing organisms
A profile sketch is like a cross section.
A Plan sketch of the same area, shows us more information about the extent of the species. (also called an areal view).
Viscosity is a resistance force (it is greater in water, than it is in land)
Buoyancy is the amount of support experienced by an object. The buoyancy of water offers support to both animals and plants. While on land, animals and plants to do not experience much buoyancy from air.
Temperature variation- (the main source of heat is from the suns radiation), water heats up more slowly than air. Surface areas on land vary far more than in water.
The earths gravitational field (the pull of gravity) gives rise to pressure differences between the upper and lower layer in both air and water. Pressure in water increases rapidly with depth. Atmospheric pressure decreases with height above sea level and also fluctuates over time- may affect breathing by animals and flight.
Oxygen and carbon dioxide are important gases for living organisms.
o Gas availability in water depends on the temperature, and diffusion is slower.
o Gases are freely available in air.
OSMOTIC (the water moves in the direction of higher concentration)
Light falling on water may be scattered, reflected or absorbed. Light is received from the suns radiation. while light can pass freely through air.
All organisms have their own requirements for successful survival and maximum growth and development. Resources- anything in an environment that organisms use. Resources are usually limited, organisms that need the same resource will be in competition.
Plants need light and water for photosynthesis- the rate of growth depends on temperature and soil or water quality.
A group of similar organisms living in a given area at the same time is known as a population.
Scientists have developed sampling techniques to make estimates of the distribution and abundance of species.
The reason population estimates are made is because of the difficulty in describing in detail any large area. It would be impractical and time-consuming to count every living thing- it would also damage the environment!
A transect is a narrow strip that crosses the area being studied, from one side to another.
A quadrant is a small area that is being selected to represent the larger area being studied.
Plant abundance- percentage cover
Animal abundance :
(method called capture-recapture)
When the number of organisms in a population increase dramatically over a short period of time, we say that there has been a population expulsion.
A food chain represents the flow of energy from one living thing to another.
Food chains begin with plants. The first consumer is called a primary consumer it is then eaten by the secondary consumer, which then may be eaten by the tertiary consumer: and so on.
When you draw a food chain, start with a producer, and point the arrows in the direction that the energy and matter flow.
Scavengers are consumers that eat dead animals. Decomposers are organisms such as fungi and bacteria that cause decay. Decomposers have an important role to play: they make the materials produced by decomposition available to plants. It is then recycled in food chains.
In most ecosystems there is more than one primary consumer, and animals often eat more than one thing. To show the complex feeding interactions in an ecosystem, we use a food web.
Biomass is the amount of living material in an organism or group of organisms at any one time.
All living things ultimately depend on the process of photosynthesis.
CARBON DIXODE +WATER (light energy + chlorophyll) sugar + oxygen
(symbol equation)
Photosynthesis is the process by which plant cells capture energy from sunlight and use it to combine carbon dioxide and water to make sugar and oxygen. It takes place in the chloroplasts of the green parts of the plants.
Chloroplasts are organelles in plant cells. Light energy comes from the sun, which is the light energy source.
All living things ultimately depend on the process of photosynthesis.
Word Equation: Carbon Dioxide + Water (light energy + chlorophyll) sugar + oxygen.
SYMBOL EQUATION
Photosynthesis takes place in the chloroplasts of the green parts of the plants.
Chloroplasts are organelles (structures within a cell) in plant cells. Light energy comes from the son, which is the light energy source.
Glucose + Oxygen Carbon Dioxide + Water + Energy (this is the respiration equation)
This process is carried out in all living cells.
Respiration is carried out in the organelle called the mitochondrion (plural=mitochondria)
Respiration involves a series of 50 different reactions= and each one is catalysed by a different enzyme.
Energy is released slowly in small amounts
THERE ARE 2 STAGES OF RESPIRATION
Stage 1 occurs in the cytoplasm.
The splitting of 6 carbon sugar molecules ( ) into two 3 carbon molecules, called pyruvate, and the making of two molecules of ATP
Stage 2 occurs in the mitochondria
It uses oxygen (which we call aerobic). The pyruvate breaks down into oxygen and water and 36 ATP molecules form.
60% of the energy is lost as heat, and 40% of the energy is glucose converted to ATP.
How is the energy from respiration used?
o Synthesis of complex molecules such as proteins, lipids, carbohydrates and nucleic acids.
o Growth involving the division, elongation and differentiation of cells.
o Repair and maintenance of damaged or old cells
o Active transport of materials across cell membranes
o Functioning of special cells that need extra energy, such as nerves, muscles, liver and kidney in mammals.
o Transport of materials within organisms, such as the phloem of plants and circulatory system of animals.
We (as humans) have disturbed many natural ecosystems to meet our own needs. However, we are quickly learning that god management of these systems is essential if they are to function efficiently. In ecosystems there is a flow of energy and materials, energy is a one-way flow, and materials are recycled.
Humans have a great impact on ecosystems. We deliberately change our environment to suit our own needs. In doing so, we bring about rapid alterations and widespread change. Our effect is often destructive to the original environment and its other inhabitants.
The removal of vegetation for farms, towns, roads and other human uses has lead to soil erosion. Crops eat up soil nutrients. Run-off from the use of fertilizers causes pollution in waterways.
Environmental pests and weeds can be controlled by physical, chemical or biological means.
PHYSICAL- control includes shooting animals and cutting down or digging out plants.
CHEMICAL- control includes use of poison baits and insecticides for animals and herbicides for plants.
BIOLOGICAL- control involves the introduction of a predator or parasite.
Pollution is the spoiling or poising of the environment though human activity.
There is a need to balance the human activities and needs in ecosystems to conserve, maintain and protect the quality of the environment.
o Many global organizations and international agreements address the quality of the environment. Greenpeace, The World Wide Fund for Nature.
o The convention on International Trade in Endangered Species of Wild Flora and Fauna (CITIES) lists those plants and animals that are not permitted for international trade.
o The national Heritage Trust (Australia now has 13 World heritage Areas)
o The World Heritage List notes those areas in the world of high importance to conserve for the future.
Role of teeth:
The action of teeth (incisors and molars) breaks down food to increase the SA:V ration for the digestive chemicals to process.
Animal cells, which are heterotrophic, must obtain food from the external environment. The digestive system is the means by which external cells are taken into the organism and broken down (digested).
The process of digestion involves the mechanical (teeth) and the chemical (saliva, digestive juices) in the breakdown of food. Complex molecules are broken down into simple molecules by specialised proteins known as enzymes.
There are three types of digestive enzymes:
Amylases- act on carbohydrates
Proteases- act on proteins
Lipases- act on lipids
Food is broken up by teeth and mixed with saliva for lubrication before swallowed. The digestion of carbohydrates may also begin in the mouth.
Relationship between herbivore and carnivore, with respect to: their chemical composition of their diet, and the functions of the structures involved.
A Carnivores digestive system is less complex and proteins can be more easily digested in the stomach.
Herbivores: need a more complex digestive system because plant material contains cellulose fibres which are harder to digest.
Structure/ Physiology Carnivore (Dog) Herbivore (Cow)
Teeth Have large canines to tear and rip meat Large flat double teeth (molars) to grind plant food
Length of time food spends in stomach (digestion) Approx 1 hour, this is a short time Approx 1 day, this is a long time
Small intestine Spread out, long, it has a large SA for absorption Long and compacted. It also has a large SA for absorption
Caecum Small; attached to side Large; because bacterial fermentation of plant material breaks down cellulose fibres. Regurgitation occurs
Faeces (water and salts that are eliminated from the digestive system) Small, dry Fibrous Faeces- more dry and large
Large Intestine Short, straight, flat Long, coiled, thinner
A herbivores diet is largely composed of cellulose. No vertebrates produce digestive fluids that can digest cellulose. Instead, micro-organisms in the colon convert cellulose into sugars. This process is extremely slow. The long colon provides increased SA for the action of microbes on the cellulose. They have complicated stomachs that consist of 4 chambers.
The Nectar feeder
The Honey possum feeds on pollen, nectar and insects. It has slender long incisor teeth and flanges on its upper and lower lips that form a channel through which a very long tongue is retracted. Nectar and pollen are scraped off the tongue as it is retracted. The digestive system is special in that a diverticulum branches off the stomach and severs as a storage container for nectar. Pollen does not appear o pass into the diverticulum but appears to be digested in the small intestine. There is no caecum.
Explain the roles of respiratory, circulatory and excretory systems:
Respiration:
Living cells need oxygen for respiration and carbon dioxide is produced as a result of respiration. When it dissolves in water, it forms carbonic acid.
We have respiratory systems to exchange gases with the external environment, and to enable cellular respiration to occur.
Circulatory:
Multicellular animals need to transport or circulate materials around their bodies to supply cells with nutrients and remove wastes (so that all cell requirements are met). The flow of materials is usually maintained by a pumping system. They can be open, or closed.
Open Circulatory Systems: (invertebrates such as arthropods and molluscs)
In insects this involves the circulation of body fluid, known as HAEMOLYMPH, (this is not blood) around the body by a simple pumping system consisting of one or more tubular hearts. Haemolymph bathes the tissues and accumulates in spaces within the insect. Any vessels that assist the transport of the fluid are open at each end. Fluid is sucked into tubular hearts through small holes. It is then pumped forwards to the front end of the insect and flows slowly backwards through the spaces surrounding the various organs. Pressure in an open system is low, so the body fluid circulates slowly.
Open Circulatory systems suit the needs of smaller animals. In insects, they do not have to transport respiratory gases, but only distribute and collect food and wastes, and sometimes store them temporarily.
[Distribution to cells/tissues: fluid flows through the tissues spaces]
Closed Circulatory Systems: (large active animals such as vertebrates and squids)
In humans, the closed circulatory system consists of a muscular pump (the heart) that forces a fluid (blood) through a closed system of tubes (blood vessels), which carry materials rapidly throughout the body. No cell in the body is very far from a blood vessel.
Distribution to cells/tissues: fluid from the blood becomes part of the body fluid which bathes all the cells.
Vessels (veins): are closed, come into and out of the heart (arteries).
Pressure: high, fast blood pumping.
Closed respiratory systems meed the need of large, active animals. They provide nutrients and oxygen to cells and carry away wastes and carbon dioxide. However, they use more energy to provide the faster service required.
Excretory:
The metabolic processes that occur in the cells of living organisms constantly produce wastes that must be removed. If not, cells would be poisoned. The main excretory products of cells are Carbon Dioxide (produced in respiration), and nitrogen (containing nitrogenous wastes produced from the breakdown of proteins and nucleic acids).
Identify the features of respiratory surfaces of multicellular animals including fish, insects, mammals and amphibians (frog)
FISH: Eg: Exposed gills hammerhead shark) Covered Gills (mullet, goldfish etc)
Respiratory surfaces are gills over which water flows. Some fish have exposed gills (eg; sharks) and others have gills covered by an operculum (eg: bony fish).
Gills are usually finely divided and the incoming water flows over a large surface area at the one time. Water flows over the gills, and then the gills open up and absorb oxygen. The blood vessels are in contact with gills.
INSECTS: Eg: Grasshoppers
Have a system of branching tubes called tracheae within their body. The tracheae is open to the external environment through pores or spirals along the abdomen. The trachea branch throughout the tissues of the insect, brining air directly to the cells. Because the insects are usually quite small, the SA of the trachea is sufficient to supply all the body cells.
MAMMALS: Eg: Humans, Kangaroo, Monkeys
In mammals, gases are exchanged in the lungs. These surfaces are protected from desiccation by being inside the bodys water-proof covering. The surface area of contact between the blood and air is increased by the convolution of the lungs into lobes, by the branching of the bronchioles into smaller tubules, and by the division of the tubules into clusters of tiny air sacs called alveoli. There is plentiful blood supply to transport gases to and from the lungs.
AMPHIBIANS: Eg: Green and Golden Bell Frog, Green Tree Frog
Have two respiratory surfaces: Lungs and Skin.
There is a very well developed blood supply to the skin. Oxygen from the air diffuses into the moist skin and is transported by the blood, to the heart from where it is sent directly to the body.
The lungs are simpler structures with a smaller surface area than those of mammals. This is why they need the skin as a respiratory surface as well.
Relationship between the requirements of cells and the need for transport systems in multicellular organisms
The more cells you have in an organism, the more transport systems that enable substances to be moved to and from the internal body cells, are needed.
Transport systems are needed by multicellular organisms to ensure that all the requirements of their cells are met.
Every cell must receive oxygen and get rid of its wastes.
Multicellular animals need to transport or circulate materials around their bodies to supply cells with nutrients, and to remove wastes.
The flow of materials is usually maintained by a pumping system. Circulatory systems may be open or closed.
1. Identify mitosis as a process of nuclear division and explain its role
2. Identify the stages of mitosis in plants, insects and mammals
3. Explain the need for cytokinesis in cell division
4. Identify that the nuclei, mitochondria and chloroplasts contain DNA
DNA is also found in mitochondria, and chloroplasts. These organelles can also replicate within a cell.
Mitosis is a type of cell division that results in the production of cells which are identical to the original cell.
The stages of mitosis:
PROPHASE (early stage): Each chromosome is visible as two identical, joined strands, called chromatids. The nuclear membrane breaks down and disappears by late prophase.
METAPHASE (middle stage): A tapered system of microtubules stretches across the cell, forming a spindle. The chromosomes line up at the centre of the cell, attached to the spindle fibres at the point known as the centromere. The chromosomes separate (In animals, the centriole is involved in spindle formation. Centrioles are absent in plants, so the spindle attaches itself to the cell wall).
ANAPHASE (toward the end stage) The Chromatids, now referred to as single-stranded chromosomes, more toward opposite poles, carried on spindle fibres.
TELOPHASE (end phase) The spindle disappears. New nuclear membranes form around the two sets of chromosomes.
The need for cytokinesis (the division of the cytoplasm- a distinction from the division of the nucleus)
Division of the cytoplasm occurs immediately after mitosis. This is necessary to ensure that the chromosome number in each cell remains constant. The chromosome number doubles in mitosis and one cell now contains two sets of chromosomes.
IN ANIMAL CELLS, THE CYTOPLASM CONSTRICTS AT THE CENTRE IN A PROCESS CALLED CLEAVAGE. A ring of microfilaments forms in the centre of the cell. As they constrict, the cell beings to cleave into two. The cell surfaces show very active movement as they separate. In plant cells, a dividing plate (the cell plate) forms across the centre of the cell, separating the two new cells (daughter cells). A new cell wall is built from this plate.
Identify the sites of mitosis in plants, animals and mammals
MAMMALS: mitosis occurs in the skin, replacing the cells that continually flake off, and causing hair/fur and nails/claws to grow. New blood cells are made every day in the bloody marrow, and in cells lining the digestive system is constantly being replaced.
INSECTS: Most insects have immature forms known as larvae. When larvae hatch from the egg, they grow and increase in size, but this is a result of cell enlargement, not cell division. In the pupal for, the larval cells break down, ad previously inactive groups of cells known as imaginal discs start to divide. They grow in both size and number to from the adult insect or imago.
PLANTS: In mature plants, mitosis occurs in the tips of roots and stems, causing an increase in length. Mitosis in special cells in the stem results in an increase in its width.
Plants continue to grow throughout their life from cells capable of mitosis known as meristematic cells.
Scientists estimate that the universe is 10-20 billion years old, and arose as a big bang, which is still expanding in the universe. Some matter in the universe condensed into solar systems called galaxies.
The early earth which originated 4.5 billion years ago, was very different and no oxygen was present. The atmosphere consisted of hydrogen, carbon monoxide, methane and ammonia.
Organic chemicals appear to have originated 4 billion years ago.
ORGANIC MOLECULES & MEMBRANES
Early organic molecules could have formed microspheres to separate living chemicals from the environment. The organic molecules react with each other making this the first metabolism. They needed to be separated from their surroundings in order to metabolize effectively so the first membranes were formed, with the lipids and proteins joining together. This lead to the first primitive cells.
PROCRAYOTIC HETROTROPHS & PROCRAYOTIC AUTOTROPHS
Prokaryotes are believed to be the first cell type. Hetrotrophs use chemicals (Carbon, and Water, from outside to gain energy and synthesis their molecules. These would use up all the biological molecules in their environment and this set up selective pressure for cells to make their own molecules from simple sources- these would be more likely to survive. These are the first autotrophs, and without them, life would have come to an end. Hetrotrophs and prokaryotes then relied on autrotrophs.
Prokaryotes consist of a cell wall, and a cell membrane enclosing cytoplasm, containing organic chemicals.
Once eukaryotic cells have evolved, they proceeded to diversity into colonies, then mulitcellular organisms;
Eventually producing plants, animals and fungi.
Success of Prokaryotes- several factors contribute to this
1. Fast rate of reproduction
2. varied metabolism
3. ability to form spores and remain dominant for years
4. use of nutrients which are inaccessible to other organism (i.e.- nitrogen)
A fossil is the remains or record of an organism that lived in the past. They provide a record over time of how things have been evolving on earth. Conditions must be right at the time of burial for an organism to become fossilised.
Fossils can tell us many things about life during the past. Using them, we can find out about species that lived long ago, and the environment in which they lived in. We can also date rocks by comparing them with fossils found at other sites.
a) Animal Fossil- Trilobite, found at kangaroo island, South Australia.
Trilobites appeared on the earth 546- 250 millions of years ago; during the Lower Cambrian age. During the Cambrian period, the climate was tropical and all life was in water. The earliest Trilobites were bottom-dwelling, crawling scavengers and mud processors. They were the most abundant and diverse species at the time, and were important animals in the oceans for over 200 million years. They lived mainly in clear, shallow seas that were teemed with life. There were over ten thousand different species of the Trilobite. Fossils of the closest relatives of Australian trilobites have been found in Malaysia, Thailand, Burma, China and the Mountains of Tibet. This suggests that these countries were once joined together.
The Trilobites name came from the division of their body. There are three divisions (central axis lobe, and two lateral lobes). The physical structure of the Trilobite is divided into three sections; the cephalon (the head), thorax and the pygidium (the tail).
They were one of the first animals to develop a hard outer covering over its body, and so fossil remains are found all over the world. Also, because of their outer covering, they were able to survive in a number of different environments.
The majority of the Trilobites were sightless. They had either single lens eyes, or compound eyes composed of a large number of discrete visual bodies. Overtime, however, they developed eyes that could see very well in dim light at the bottom of the sea.
The optimum time for the Trilobite was reached during the Late Cambrian. Then afterwards, their numbers began to decline perhaps in response to predation from cephalopods and fishes, and possibly drying of the land. They were extinct near the close of the Paleozoic.
It can be deduced that the land during the Cambrian age was fairly moist, as the Trilobites lived in watery environments. It can also be thought that towards the Paleozoic era, the land began to dry, as the trilobites became extinct.
Trilobites do not exist today and this tells us that the environment long ago is a lot different than the environment today.
b) Plant Fossil- Ferns, (Pterospids) found at South Gippsland and the Otway Ranges in Victoria.
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Ferns (Pterospids) were widespread in the Carboniferous age (more precisely, the Pennsylvanian time) and became extinct in towards the end of the Tertiary period. It was known as the Age of Ferns as they were both abundant and diverse, and were also a dominant part of the vegetation at that time. The were among the oldest kinds of plants that lived on land.
They were common in coal swamps. They could live in a diverse range of environments; however the spores could only germinate in very damp conditions. So, it can be deduced that where ferns were found, water must have been present.
They ranged in size from the small, delicate plants found in temperate climes to the big-leafed tree ferns of the tropics. Ferns have a well-developed vascular system; clear differentiation into roots, stems and leaves.
Today however, a number of different types of ferns exist (the ferns that existed during the Carboniferous age are now extinct). [Today, fern is a common name for any of a division of cryptogamous (spore-producing) plants.] This also tells us, that the environment long ago is different from that of today.
Oparin
In 1924, Russian biochemist Oparin proposed that life had arisen from simpler molecules on the lifeless earth under much different atmospheric conditions than those that exist today; over a long time.
Haldane
In 1929, English biologist Haldane published a paper in which he proposed that ultraviolet light (from the sun), when acted upon the Earths primitive atmosphere, produced a vast array of organic compounds (ammonia, hydrogen, methane with water). These compounds accumulated in oceans until they had the consistency of a hot dilute soup.
Haldane and Oparin believed that life could have evolved in the conditions of the early earth.
In conclusion; Oparin and Haldane made a hypothesis about the origin of life, and Urey and Miller provided the evidence by conducting an experiment as outlined below.
Urey and Miller
In 1953, Urey and Miller performed their famous experiment whilst working at the University of Chicago. They wanted to test if it was possible for organic molecules to have formed in a reducing and energy-rich environment similar to the early earth . Many say that they proved life can come from chemicals. Their work tied in with Albert Einsteins work and Charles Darwins theory of evolution. They started with the components of the Earths primitive atmosphere (methane, ammonia, hydrogen and water) and placed these in a five litre boiling flask, an in the apparatus shown below. They also ran a continuous electric current through the system, to simulate lightening storms that were believed to be common in the primordial earth. Boiling water produced steam, which helped to circulate the gasses through the system.
They left this apparatus for one week, then analysed the water containing organic compounds.
Products of the Miller and Urey Experiment:
Tar 85%
Carboxlic acids not important to life 13.0%
Glycine 1.05%
Alanine 0.85%
Glutamic Acid Trace
Aspartic Acid Trace
Amino acids are more commonly known as building blocks, as they are required in the manufacture of protein, which are essential for growth and repair. There are fifty known amino acids, four of these fifty occurred in this experiment (Glycine, Alanine, Glutamic acid and Aspartic acid). So, a number of substances related to life were synthesized as a result of the above apparatus. It is evident from the results that organic molecules were produced in the simulated conditions.
Miller and Urey concluded that life can come from inorganic substances.
The importance of their experiment in showing the nature and practice of science is apparent. They had proposed a model and through experimentation, it was demonstrated that the model could have correct. Miller and Ureys experiment was repeated a number of times by various scientists, and each time they changed a variable, no amino acids resulted.
Their contribution to hypothesis about the origin of life helped many scientists in future decades. They provided the experiment (and inturn support) for Haldane and Oparins theories about how the first organic molecules could have formed.
In sexual reproduction, sex cells must be transferred from where they are made to where they can join.
There are two types of fertilisation.
a) External Fertilisation
In this method, the egg and sperm unite outside the bodies of the parents. This is usually the case with most aquatic organisms such as; sea urchins, starfish, clams, mussels, frogs, corals and many fish.
The gametes are released into an ocean or pond, where embryos begin to develop. The meeting of the egg and sperm is left to chance as swift water currents, temperature changes and predators can prevent fertilisation. As a result, millions of sperm and egg are produced. This way, even if a fraction of the sperm and egg meet, several offspring will still result.
Example of External Fertilisation: Frogs
Eggs contain all the food and protection needed for the growth of a new animal. A simple diagram of an egg is outlined and explained below.
However, not all external-reproducing organisms have eggs like this. As shown above, the eggs of fish are light and transparent due to the risk of being eaten. Reptiles and birds produce shelled eggs to try to overcome the difficulties and threats on land. It also seems that many eggs that develop on land, have developed their own natural sunscreens, as a protection from the sun.
b) Internal Fertilisation
Organisms that are on land, face the problem of sex cells and the developing zygote drying out. So, in most multicellular land organisms, the female sex cell is fertilised inside the female organism. This occurs within the females body. This type of fertilisation is more common with terrestrial organisms such as; mammals, reptiles, birds as well as some invertebrates including snails, worms and insects. The male typically has a penis or other structure that can effectively deliver sperm into the females reproductive tract.
However, in internal fertilisation, the sperm and egg are always protected in both the males and females bodies, and are placed in close contact during mating. Because of this, few sperm and egg are produced.
Example: Internal Fertilisation- Human (Mammals)
Pre-Labor
Placenta increases its surface area, to
increase flow of nutrients,
and disposal of wastes.
Blood supply to uterus increases, to supply
nutrients to the embryo. Breast size increases, carrying milk for the baby.
During Labor:
Pelvic joints become loose to allow a passageway for the foetus.
Uterine muscles begin to contract at regular intervals. As the time between contractions becomes shorter, the contractions become longer and more intense
Forceful uterine contractions push the foetus from the uterus, through the birth canal
The foetus head moulds- to allow for an easier delivery.
Post Labor:
After birth, the placenta separates from the uterine wall and is expelled. This is to prevent bleeding.
In addition, the baby is born with a sucking ability, so when he/she sucks on the mothers breast it stimulates the brain, which releases hormones and inturn stimulates the mothers chest to produce milk. Mammals, (especially humans) also tend to take great care of their young after they are born.
SPEECH ON FOSSILS:
For my plant fossil I picked the ferns, and these can be found along the east coast of Australia. These were found in South Gippsland and the Otway Ranges in Victoria. They were widespread in the Carboniferous age, as this was known as the age of ferns, as they were both abundant and diverse, and were also a dominant part of the vegetation at that time. They became extinct towards the end of the tertiary period.
They were very common on coal swamps. They could live in a diverse range of environments, however they could only reproduce in watery conditions. Therefore, it can be deduced that were these plants were found, water must have been present.
They ranged in size from the small delicate plants, to the big leaded tree ferns of the tropics.
Today, these ferns are extinct, and the word fern is now a common name for any division for spore-reproducing plants. This tells us, as with the trilobite (as they are both extinct) that the environment and species that live today are very different from those that lived long ago.
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