Sample HSC questions Flashcards
Describe the role and changes in levels of a hormone in pregnancy.
A hormone that is important in pregnancy is progesterone. Progesterone is initially produced by the corpus luteum in the ovary and causes the endometrium to thicken, which helps to support and maintain the pregnancy in the first weeks when the placenta is still developing. The developed placenta then produces progesterone at significantly higher levels to maintain the pregnancy. Prior to birth progesterone levels drop significantly to facilitate labour.
Justify why internal fertilisation is more advantageous than external fertilisation in ensuring the continuity of a species.
For the continuity of a species, each generation must successfully reproduce to produce sufficient numbers of the next generation. A critical number of embryos must survive to gestational maturity. This is less likely with external fertilisation.
Organisms that reproduce by external reproduction spend a substantial amount of energy and resources in the production and release of very large numbers of sperm and eggs. This is because each sperm and egg and the resulting embryos have limited chances of survival, not being protected by the parent for example in the open ocean. Chances of successful fertilisation are low in such vast aquatic environments. Larger numbers ensure some will be fertilised.
Internal fertilisation provides a smaller safer environment for release of gametes, fertilisation and maturation of the embryos. Chances of successful fertilisation are increased and embryos are protected from predators within the body of the parent. Even after birth/egg laying parental care assists survival of the offspring.
Mutagen definition:
A mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level.
Examples of mutagens:
Types of mutagens can include radiation and chemicals. Benzene is an example of a chemical mutagen. Benzene binds DNA, inhibits DNA synthesis and causes double strands to break, leading to aberrations in genes and chromosomes.
Kakadu Plum
For example, the Kakadu Plum is an important bush food for people in northern Australia; the fruits and seeds were eaten raw and used to treat colds and flus. Scientists have discovered that the Kakadu Plum fruit contains the highest recorded level of natural vitamin C of any plant globally, more than 100 times that of oranges and therefore has enormous potential for use in dietary supplements and health foods.
Epidemiology studies
Epidemiological studies are used to find the causes of health outcomes and diseases in populations and are vital in our understanding of non-infectious diseases and how to address them.
Epidemiological studies can determine causation of a disease. By conducting descriptive studies, cohort studies and control studies, strong correlations between particular factors and the incidence of a disease can be discovered and explored to try and establish causation. Once causation of a particular disease is understood, strategies for preventing it and/or limiting its incidence and/or mortality rates can be developed. Descriptive studies can allow epidemiologists to discover what groups within a population are most likely to be affected by a non-infectious disease. This allows any interventions made, e.g, by government health departments to be more efficient because they are being targeted at the groups in society who most need it. One downfall of epidemiological studies is that the quality of the data they produce very much depends on the quality of the study and design and biases.
Types of proteins:
Structural proteins are responsible for support for cells and their organelles and also provide support to major structures such as cartilage and hair. Examples include collogen and keratin. Functional proteins are involved in biochemical reactions and help maintain normal immune function. Examples include enzymes (e.g. avidin) and immunoglobins.
Normal vision, myopia, and hyperopia
In normal vision, the light can be seen being refracted through the cornea, aqueous humour, lens, and vitreous humour and coming to focus on the retina, which converts the light energy into electrochemical impulses that are sent through the optic nerve to the occipital lobe of the brain for processing.
Myopia – the eyeball is too long, and the light focuses in front of the retina, causing the image seen to be blurred/ not sharp.
Hyperopia – either the eyeball is too short, or the lens is not able to retract light sufficiently and the focal point of light entering the eye is behind the retina, again causing the image seen to be blurred/ not sharp
Artificial pollination
Artificial pollination is the dusting, often by hand of fertile stigmas with the pollen from plants with desired characteristics
Artificial insemination
Artificial insemination is the injection of male semen into a female of the same species.
Ethical consideration of Bt cotton
Bt cotton is an example of a transgenic species created by scientists. It provides a benefit to society as it reduces the need to spray cotton crops with insecticides. This saves people time and money; it also means that crops are more successful and there is greater yield for use by humans (as clothing) and animals (as a feed supplement). An advantage to the environment is that Bt cotton reduces the use of insecticides, which benefits food chains and food webs. One disadvantage of this crop is that farmers have to buy the seeds each year and are dependent on large companies. Another disadvantage of Bt cotton is that it reduces biodiversity as it means large areas of crops are genetically identical; it Is also potentially toxic to non-target animals.
Ethical consideration of transgenic salmon
transgenic salon with the BGH (Bovine Growth Hormone) gene incorporated in its genome. An advantage of these fish growing faster is there are higher yields and profitability for fisheries. Another advantage for society is that there is more product available for commercial use which could also lead to cheaper salmon meat for consumers. A disadvantage is that the fish have to be kept in pond, which may not be conductive to maximising their health. Another disadvantage is that they may destroy natural ecosystems if they make their way in to river systems.
Benefits of the continued use of genetic technologies
Benefits of the continued use of genetic technologies used for the direct modification, removal or transfer of gene/s or other genetic material microorganisms and plant-based substances are now being manipsulated using genetic technologies to benefit society via medical treatments. For example, mRNA technologies have been enabled the production of vaccines, such as the COVID-19 vaccines. The mRNA encodes a key protein of SARVS-COV-2; once the mRNA gets inside our cells, our bodies produce this protein. That acts as the antigen, the foreign molecule that triggers an immune response. Genetic technologies have also enabled the creation of bacterial-medicated cancer therapies to assist in the treatment of various cancers by using the bacteria as vectors for therapeutic cancer medication.
Both medical examples have positive benefits to society via increasing the health of induvial (and therefore their ability to contribute positively to society) and through the reduction in the healthcare and societal costs associated with disease.
Stages of Darwin’s Theory of Evolution by Natural Selection
Stages of Darwin’s Theory of Evolution by Natural Selection:
1. There is genetic variation in population, which affects it phenotype (physical traits). The genetic variation is derived from a number of factors – from internal biological processes to external environmental factors. These factors will be comprehensively covered in later weeks.
2. The majority of the existing population would have the favourable traits that allow them to survive in the environmental conditions (temperature, food supply, predators, etc) that they are exposed to.
3. There is a SUDDEN change in environmental conditions (e.g. new predator introduced to kill the unicorns, sudden large drop in temperature, a virus, etc)
4. Those organisms with favourable characteristics, derived from favourable genes passed on from parents, will survive and those with less or without favourable characteristics will decline in numbers.
5. Those organisms with favourable characteristics will reproduce more successfully and pass on their favourable genetic information to their offspring. REPRODUCTION FITS IN HERE!
6. Over time, the new population will predominately be made up of organisms with favourable characteristics that allow them to tolerate the new environmental conditions.
The environmental agent is refers to the environmental change. This could be a exotic species introduced into the habitat (e.g. from migration) that is competing for the same food resource as the existing population, a new predator, introduction of chemicals into the environment – e.g. toxic wastes being throw into the river, home to thousands of fish..
It is called Darwin’s Theory of Evolution by Natural Selection because there is a sudden change is due to environmental (nature) change(s).
Favourable characteristics that allow organisms to survive in their environment can take three forms: Physical, Physiological and Behavioural.
‘Favourable’ means that these characteristics allow the organism to specifically or better cope with its ambient environment. An organism CANNOT adapt to its environment during its lifetime. Adaptations are inherited.
Internal vs external fertilisation:
Internal fertilisation involves the fusion of male and female gametes within a parent’s body. Internal fertilisation tends to occur between terrestrial animals.
External fertilisation involves the fusion of male and female gametes outside a parent’s body. External fertilisation tends to occur between aquatic animals.
Parthenogenesis
Parthenogenesis is the process whereby an unfertilised egg develops into an functional offspring. This is a form of asexual reproduction in animals, e.g. bees.
Cross pollination vs self-pollination
Cross pollination involves the transfer of pollen, produced by anther (which is part of the plant’s stamen), to the stigma of another plant. This means that cross pollination involves two plants. Bees, wind and water can be transport methods of pollens grain to stigma of another plant for cross pollination.
The difference between self-pollination and cross-pollination is that self-pollination does NOT involve a an external agent such as bees, water and wind as mentioned previously. Instead, the stigma can reshape itself to enclose the stamen. This means that the pollen can be easily transferred onto the stigma. Self pollination causes the resulting flower offspring (after seed germination) to have far less genetic variation than their parents in most cases compared to cross pollination. This is because the resulting flower is only produced from only one parent plant rather than two in cross pollination.
Vegetative propagation
Vegetative propagation is a type of asexual reproduction that occurs in plants. It results in the parent producing a plant that is genetically identical. Runners, bulbs, fragmentation.
Fragmentation
Fragmentation is when the original organism separates a small part of itself. This occurs in starfish where a part of its body can be separated from its parent and the separated section can develop into a new starfish that is genetically identical to parent starfish via cell division.
runners
Strawberry plants can develop runners which are stems extending from the plant and along the soil. At certain points along the runners, nodes can develop which extends to the soil, resulting in the formation of new plant roots at another area of the soil whereby a new strawberry plant can grow. The runner joins the new (and genetically identical) strawberry plant to the parent plant.
buds
Bulbs are bud cells that are found underground. These buds can develop into new plants such as onions. When a new plant forms, the underground bulb provide nutrients to the plant for its survival.
Artificial insemination
It involves a male sperm cell being inserted into a female’s reproductive tract. The fusion of the sperm and egg cell results in fertilisation of the egg cell, producing of zygote. Artificial insemination is primarily used to produce offsprings with favourable characteristics, mix of both male and female parents. Artificial insemination is a form of selective breeding because it allows the sperm cell of a selected male to fertilise the egg cell of a selected female.
Artificial pollination
Artificial Pollination involves the manual transfer of pollens into stigma of another plant to combine with the egg cell (ovule) of the plant.
Cloning:
Cloning is a type of asexual reproduction used to create offsprings that are genetically identical to the parent.
Dolly clonning example
In 1988, Dolly the Sheep is an offspring that was a clone offspring. Dolly was successfully cloned using a sheep’s (sheep A) mammary gland (a group of somatic/body cells). The scientists then removed the nucleus (therefore DNA) of another sheep’s (sheep B) egg cell and inserted the nucleus of the somatic cell from the mother sheep into the egg cell. The egg cell undergoes cell growth and development inside a foster mother sheep (sheep C) to produce Dolly the Sheep. Dolly the Sheep has the same genetic information as Sheep A (inherited Sheep A’s genetic information) and thus is a clone of Sheep A. However, Dolly the Sheep died earlier than scientists’ expectation. This led to questions relating to health and ethical problems of cloning.
Distinguish between sexual reproduction and asexual reproduction
Sexual reproduction, such as meiosis, is the process of forming a new organism from the fusion of the offspring’s parents’ gametes. Comparatively, asexual reproduction, such as mitosis, is the process of producing an offspring from just one parent through cell division or mitosis.
The offspring as a result of sexual reproduction does not have genetic material that is identical to its parents. The offspring from asexual reproduction is a clone of its parent, meaning it has the same allele combinations as its parent.
Describe how reproduction fits into Darwin’s Theory of Evolution by Natural Selection
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 favourable characteristics which is derived from their genetic information. Those species with favourable characteristics to tolerate the 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, mismatch of nitrogenous bases during DNA replication as well as the random fusion of gametes contribute towards the genetic variation in a species’s population.
Secondly, the mechanisms of meiosis allows parents’ DNA, coding for favourable characteristics, to be passed on to their offsprings. Those species with favourable characteristics for the new environment will survive and reproduce more successfully than those without. This is critical in Darwin’s Theory to explain the shift in a population’s dominant characteristics over time due to selective pressures.
Explain how the continuity of a species is achieved and maintained
environment and avoid extinction in general. This can be explained by how the processes of crossing over, random segregation, independent assortment increases the genetic variation of offsprings in a population whenever meiosis occurs. This increase in genetic variation means that there are more allele combinations and, thus, more unique adaptations. A population of species with more unique adaptations would mean greater chance of a characteristics that would be favourable in tolerating changes in environmental conditions. Thus, the increase in genetic variation would reduce the probability of mass extinction and ‘ensures’ (supports) the continuity of a species.
Define the term ‘environmental agent’ and provide an example
An environmental agent is a selective pressure in the ambient environment for a population of species. This environment agent determine the favourable characteristics in a population. An example of an environment agent can be a predator (e.g. Leopard) for a rabbit population.
Define the term ‘adaptation’
Adaptation are the inherited favourable characteristics of an offspring from its parent(s). These characteristics may be physical (Structural), physiological or behavioural.
structural adaptations
Structural adaptations refer to physical characteristics of an offspring. An example of this may include the long ears of Red Kangaroos that aid cooling. (You will learn more about this in later modules)
physiological adaptations
Physiological adaptations refer to the biochemical processes that an organism is able to perform to allow it to tolerate its ambient environment’s selective pressures. An example of this is how echidna can decrease its heart rate to reduce the oxygen it consumes per minute when they are swimming to escape floods.
Behavioural adaptations
Behavioural adaptations refer to how an organism moves to respond to a threat, need or any other event to ensure the continuity of the species. An example of a behavioural adaptation is how snakes seek shade (e.g. under rocks) during a hot summer day to prevent overheating so enzymes do not denature.
Outline the process of binary fission
Binary fission is an example of an asexual reproduction process. First, the somatic cell’s genetic material is duplicated which is then followed by the separation of the somatic cell into two daughter cells. The two daughter cells are clones of the parent somatic cell, that is, they both have identical genetic information as their parent.
Crossing over
During prophase 1 crossing over occurs are maternal and paternal chromosomes line up along side one another. The arms of the chromosomes intercept is called chismata, in chismata the genetic information swaps ‘synapsis’ and this increases variation occurring with new allele combinations
Independent Assortment
Independent Assortment occurs during Metaphase I of Meiosis I. Independent assortment is the process where the alleles specifying for different genes (in non-homologous chromosomes) assort themselves independently.
Random Segregation
Random Segregation of chromatids (chromosomes) occurs in Anaphase II of Meiosis II. Independent Assortment in Metaphase I results in the separation of double-stranded CHROMOSOMES from their homologous pairs in Anaphase I. Random Segregation deals with separating CHROMATIDS of EACH double-stranded chromosome.
Independent Assortment vs Random Segregation
independent assortment deals with sorting of alleles of different genes in non-homologous chromosomes and random segregation deals with splitting of double-stranded chromosomes to single-stranded chromatids (where each chromatid may have different alleles for a particular gene).
Nucleotide composition, hydrogen bonding and pairing
- DNA is a polymer made up of nucleotide monomers
A nucleotide contains a deoxyribose sugar joined to a phosphate group and a nitrogenous base - The sugar-phosphate chain forms an external backbone for the DNA strand and the nitrogenous bases radiate towards the centre of the helical molecule, joined to the sugar in the backbone
- Two purine bases: Guanine (G) and adenine (A) and two pyrimidine bases - thymine (T) and cytosine (C) - are the nitrogenous bases.
- Hydrogen bonding results in the nitrogenous bases paring A-T and C-G
Difference between DNA and RNA
- RNA has the sugar ribose present, whereas DNA has the sugar deoxyribose
- Uracil pairs with adenine in RNA, while thymine pairs with adenine in DNA
- RNA consists of a single strand, whereas DNA consist of a double strand
DNA in prokaryotes
Circular chromosome (contains DNA). DNA is not wrapped around proteins
DNA in eukaryotes
Have linear chromosomes in nucleus. DNA in mitochondria are circular. DNA in chloroplast can be linear or circular
Transcription
The process of turning genetic information stored in the DNA into an intermediary molecule (mRNA)
- DNA polymerase binds to the ‘promotor’ which signals the DNA to unwind and allows enzymes to read the bases
- The mRNA molecule is built using the complementary bases
- The mRNA molecule detaches from the DNA strand
Translation
the process where genetic information encoded as mRNA turns into a polypeptide chain
- mRNA attaches to a ribosome
- the ribosome attaches the codons and anticodons together
- polypeptide chain forms and grows as amino acids are added
- once a stop codon is reached, the chain detaches
mRNA
mRNA is important in ensuring the correct gene will allow the correct mRNA, formed from complementary base pair, to specify the correct tRNA carrying a specific amino acid to bind with the matching mRNA codon. This ensures that the right amino acids sequence of the resulting polypeptide chain and, hence, the correct protein to be created.