2019 HSC Biology Marathon (1 Viewer)

[ConquerHSC]

Hey hey hey!

Welcome to the HSC Biology Marathon if you sitting the HSC Biology Exam in 2019!

A prior HSC Chemistry Marathon has already set out the rules of HSC marathons. So I am just going to copy the rules from the 2016 HSC Chemistry Marathon (old syllabus).

http://community.boredofstudies.org/17/chemistry/344627/hsc-2016-chemistry-marathon.html

"So, here are the copied rules:

This thread is an open chain of questions between students. It works by answering a question then posting another question and allowing the cycle to repeat itself as this is used to test others!

Just some simple rules:
- Answer the question asked previously, before posting a new question.
- After you have answered a question, post another question to keep the thread alive (or else I have to come in and post a new question)
- try to allocate a number of marks for any question that you post.

Tips:
- It may help to write your answers on paper before typing them on this thread as it will mirror your exam.
- You may post more than one question.
- When possible, after questions have been answered, you can peer mark using the marking scheme.

For future reference, please refrain from using this thread for help. Instead I'd suggest you make your own individual thread in the Biology Section of this forum if you want help.

Also, please refrain from derailing this thread. If you want to talk about a specific topic or whatever to someone else, please do it via PM or have the conversation somewhere else as we want the marathon running smoothly"

Let's #conquerhsc together! ~

 

[ConquerHSC]

Let me start us off with some questions

1. Explain Darwin's Theory of Evolution by Natural Selection supports the continuity of a species [6 marks]

2. Explain how an organism derives its favourable characteristics [3 marks]

3. Describe the advantages of internal fertilisation and external fertilisation [4 marks]

I will post my answers to these questions in 48 hours.

Please give the questions a go I will DM you my feedback and solutions once you have posted your solution (if you reply within 48 hours).

Remember, once you have answered the question, please post another question so I (and other students) can answer it and test ourselves!

2019 HSC is going to be an awesome year!

Let's learn lots from each other and #conquerhsc together! Let's gooo!~

 

[pikachu975]

Let me start us off with some questions

1. Explain Darwin's Theory of Evolution by Natural Selection supports the continuity of a species [6 marks]

2. Explain how an organism derives its favourable characteristics [3 marks]

3. Describe the advantages of internal fertilisation and external fertilisation [4 marks]

I will post my answers to these questions in 48 hours.

Please give the questions a go I will DM you my feedback and solutions once you have posted your solution (if you reply within 48 hours).

Remember, once you have answered the question, please post another question so I (and other students) can answer it and test ourselves!

2019 HSC is going to be an awesome year!

Let's learn lots from each other and #conquerhsc together! Let's gooo!~

What have you guys learned so far in terms of which dot points? If you tell me I'll try post some questions for you!

 

[ConquerHSC]

Response to Question 1:

Darwin’s Theory of Evolution by Natural Selection states that new selective pressures introduced in an environment will alter a species’ population based on the species’s genetic variation. Those species with favourable characteristics to tolerate the new conditions will survive and reproduce more successfully than those without.

Part of Darwin’s Theory of Evolution states that genetic variation is present in a population. Reproduction processes such as meiosis can be used to explain the origin of such variation. More specifically, during meiosis, the processes of independent assortment, crossing over, random segregation, mutations leading to changes in DNA sequence, as well as the random fusion of gametes can contribute towards the genetic variation of a species.

A population with increased genetic variation will allow the species to minimise the chances of mass extinction as there new allele combinations are inherited by offspring that may allow them to tolerate against the new environment selection pressures. Over time, as per Darwin’s theory of evolution, these offsprings with favourable characteristics will reproduce more successfully than those without and dominate the population. Hence, Darwin’s theory of Evolution explains how the increased genetic variation via reproduction and heredity of such variation by offspring supports the continuity of a species.


Response to Question 2:


Favourable characteristics are adaptations that allow an organism to effectively tolerate the selective pressures in its ambient environment. An organism’s adaptations are inherited from its parent(s) via asexual or sexual reproduction. During reproduction, the parents’ genetic material, coding for adaptations, are passed onto the offspring.


Response to Question 3: (Only need 2 of each kind)

Internal fertilisation


Advantages:
• Internal fertilisation typically have less mating partner options than internal fertilisation. This can lead to a lower genetic variation in species population as the mating process is more selective than external fertilisation
• Internal fertilisation occurs inside the female's body which means that the zygote is protected from the external environment of the parent. This means there are less environmental factors that affect the zygote in internal fertilisation compared to external fertilisation. This increases the survival of the zygote.
• Internal fertilisation is NOT restricted to aquatic environment unlike external fertilisation
Internal fertilisation has higher fertilisation success rate on a per gamete basis compared to external fertilisation. This is because the sperm does not need to travel by chance to fertilise an egg. Internal fertilisation provides the sperm a direct route towards to egg cell inside the female's body. During such journey, the sperm cell is subjected to less variable and/or violet environment factors such as strong current or predators.

External Fertilisation

Advantages:
•*Greater quantity of gametes are produced via external fertilisation compared to internal fertilisation. This leads to a greater overall amount of offsprings produced. Arguably, this could supports the continuity of species more than internal fertilisation.
•*External fertilisation can give raise to more mating partner options than internal fertilisation. This can lead to greater genetic variation in species population as the mating process is less selective than internal fertilisation.*


New Question: Explain in what scenarios will artificial reproduction methods increase and decrease genetic variation in a population of rainbow unicorns [4 marks]

New Question: Explain the role of hormones before fertilisation and in sustaining pregnancy [8 marks]

 

[ConquerHSC]

Response to Question: Explain the role of hormones before fertilisation and in sustaining pregnancy [8 marks]

Prior to fertilisation, as per normal menstrual cycle to prepare for pregnancy, GnRH is secreted in response to low levels of progesterone and oestrogen from the hypothalamus to stimulate the pituitary gland. This results in the pituitary gland to release follicle stimulating hormones (FSH) and luteinising hormones (LH) to encourage follicle (and its containing oocytes) to develop inside the ovaries. As follicles mature, they secrete oestrogen into the blood stream which releases in a spike in LH level. This spike in LH level will result in ovulation where the matured egg is released from the developed follicle. The empty follicle will collapse to form the corpus lute which further secretes oestrogen and progesterone, preventing any further production of FSH of LH.

The mature egg will migrate to the ovary’s surface and eventually into the fallopian tube where it will be moved by cilia along the tube and into the uterus. It is in the fallopian tube whereby the sperm may encounter, interact and fertilise the matured egg. Once the cilia moves the matured egg cell into the uterus, it will be implanted onto the uterus walls (endometrium).

Upon successful implantation, it will encourage the corpus luteum to secrete more oestrogen and progesterone. LH will also be produced by the pituitary gland which will encourage further progesterone production from the corpus luteum resulting in a spike progesterone level. The oestrogen will help develop the placenta.

The progesterone will stimulate the glands in the endometrium which secretes mucus to thicken the uterus lining until placenta forms. Other nourishing substances secreted by the glands will help sustain the embryo by supplying it with oxygen and nutrients.

About three months in, the placenta takes over the hormone secretion role of the corpus luteum where the secretion of progesterone and oestrogen will decreases towards birth of offspring. Progesterone suppresses urinal activities to reduce disturbance that may otherwise affect the development of embryo into foetus. The placenta will also produce HCG to sustain the corpus luteum which is the reason why HCG levels are high when tested for pregnancy.

However, during this time, the placenta will provide the pathway in which carbon dioxide and urea can be eliminated from the foetus into the endometrium via diffusion and secreted out of the mother’s body. The placenta also supplies the blood (oxygen and nutrient) required by the foetus to sustain pregnancy.

 

[ConquerHSC]

Distinguish the nature, and named examples, of physical, chemical and naturally occurring mutagens [3 marks]