Sample HSC questions

Question 1

Describe the role and changes in levels of a hormone in pregnancy.

Answer 1

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.

Question 2

Justify why internal fertilisation is more advantageous than external fertilisation in ensuring the continuity of a species.

Answer 2

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.

Question 3

Mutagen definition:

Answer 3

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.

Question 4

Examples of mutagens:

Answer 4

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.

Question 5

Kakadu Plum

Answer 5

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.

Question 6

Epidemiology studies

Answer 6

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.

Question 7

Types of proteins:

Answer 7

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.

Question 8

Normal vision, myopia, and hyperopia

Answer 8

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

Question 9

Artificial pollination

Answer 9

Artificial pollination is the dusting, often by hand of fertile stigmas with the pollen from plants with desired characteristics

Question 10

Artificial insemination

Answer 10

Artificial insemination is the injection of male semen into a female of the same species.

Question 11

Ethical consideration of Bt cotton

Answer 11

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.

Question 12

Ethical consideration of transgenic salmon

Answer 12

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.

Question 13

Benefits of the continued use of genetic technologies

Answer 13

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.

Question 14

Stages of Darwin’s Theory of Evolution by Natural Selection

Answer 14

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.

Question 15

Internal vs external fertilisation:

Answer 15

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.

Question 16

Parthenogenesis

Answer 16

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.

Question 17

Cross pollination vs self-pollination

Answer 17

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.

Question 18

Vegetative propagation

Answer 18

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.

Question 19

Fragmentation

Answer 19

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.

Question 20

runners

Answer 20

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.

Question 21

buds

Answer 21

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.

Question 22

Artificial insemination

Answer 22

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.

Question 23

Artificial pollination

Answer 23

Artificial Pollination involves the manual transfer of pollens into stigma of another plant to combine with the egg cell (ovule) of the plant.

Question 24

Cloning:

Answer 24

Cloning is a type of asexual reproduction used to create offsprings that are genetically identical to the parent.

Question 25

Dolly clonning example

Answer 25

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.

Question 26

Distinguish between sexual reproduction and asexual reproduction

Answer 26

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.

Question 27

Describe how reproduction fits into Darwin’s Theory of Evolution by Natural Selection

Answer 27

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.

Question 28

Explain how the continuity of a species is achieved and maintained

Answer 28

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.

Question 29

Define the term ‘environmental agent’ and provide an example

Answer 29

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.

Question 30

Define the term ‘adaptation’

Answer 30

Adaptation are the inherited favourable characteristics of an offspring from its parent(s). These characteristics may be physical (Structural), physiological or behavioural.

Question 31

structural adaptations

Answer 31

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)

Question 32

physiological adaptations

Answer 32

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.

Question 33

Behavioural adaptations

Answer 33

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.

Question 34

Outline the process of binary fission

Answer 34

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.

Question 35

Crossing over

Answer 35

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

Question 36

Independent Assortment

Answer 36

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.

Question 37

Random Segregation

Answer 37

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.

Question 38

Independent Assortment vs Random Segregation

Answer 38

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).

Question 39

Nucleotide composition, hydrogen bonding and pairing

Answer 39

• 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

Question 40

Difference between DNA and RNA

Answer 40

• 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

Question 41

DNA in prokaryotes

Answer 41

Circular chromosome (contains DNA). DNA is not wrapped around proteins

Question 42

DNA in eukaryotes

Answer 42

Have linear chromosomes in nucleus. DNA in mitochondria are circular. DNA in chloroplast can be linear or circular

Question 43

Transcription

Answer 43

The process of turning genetic information stored in the DNA into an intermediary molecule (mRNA)

1. DNA polymerase binds to the ‘promotor’ which signals the DNA to unwind and allows enzymes to read the bases
2. The mRNA molecule is built using the complementary bases
3. The mRNA molecule detaches from the DNA strand

Question 44

Translation

Answer 44

the process where genetic information encoded as mRNA turns into a polypeptide chain

1. mRNA attaches to a ribosome
2. the ribosome attaches the codons and anticodons together
3. polypeptide chain forms and grows as amino acids are added
4. once a stop codon is reached, the chain detaches

Question 45

mRNA

Answer 45

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.

Question 46

tRNA

Answer 46

tRNA’s role is important in ensuring that it’s anticodon specifies and binds to the correct amino acid. This will ensure that the resulting polypeptide chain will have the right amino acid sequence that allow the protein-folding process to occur correctly

Question 47

enzymes

Answer 47

Without enzymes, many metabolic processes such as cellular respiration simply will not occur as the reactants will not form chemical bonds with each other to create the products.
The enzymes involved in catalysing mammals’ metabolic processes are proteins. Enzymes allows reactions to occur with lower energy at faster rates. Enzymes work by binding reactants together at the enzymes’ active site to weaken their chemical bonds and create products.
The enzyme’s active site is critical in ensuring that the enzyme is able to attach the specific reactants by their specific shape. The enzyme’s active site and the specific reactants’ shape matches specifically! So, if the enzymes’ (protein) shape is not correct due to incorrect amino acid sequence in protein synthesis, the enzymes’ (protein) cannot correctly perform its function in catalysing the required metabolic process such as cellular respiration.
Without cellular respiration, the cells of the organism will not be able to able ATP (Energy).
Haemoglobin is a protein molecule that is inside our red blood cells are continuously produced in the bone marrow. Haemoglobin is a protein that is made up of four polypeptide chain and helps increase the amount of oxygen that our red blood cells can carry to our cells for cellular respiration.

Question 48

Relationship between environment and phenotypic expression

Answer 48

The organism’s diet or availability of food/water: Pea plants that have limited availability of water would be shorter than pea plants that have access to abundant volumes of water, provided their pea plants are genetically identical.
pH of soil: Hydrangeas exhibit pink and blue colours depending on the pH of the soil. If the soil pH is less than 6, the hydrangeas will be blue. If the pH is greater than 7, they are pink. Hydrangeas colour are dependent on the concentration of aluminium ions in the soil where ion availability is affected by pH.
Temperature of ambient environment: Himalayan rabbits are found to have different fur colour based on temperature affecting their gene expression in producing fur pigments. Above thirty five degrees celsius, they have white fur (better at reflecting heat). Below thirty degrees celsius, they have black fur (better at absorbing and trapping heat).

Question 49

Mutation

Answer 49

Mutation, however, alters the allele’s identity because the DNA sequence is altered. This new DNA sequence can lead to an alternative expression of the gene (e.g. blue eye colour instead of black eye colour), hence new allele (different DNA sequence for same gene) is created.

Question 50

Co-dominance

Answer 50

Co-dominance occurs when both alleles for a trait are expressed at the same time without blending of the trait that each allele specifies. This occurs when there is no recessive alleles for the trait.
An example of co-dominance is when a cow have both red and white colour patches on its skin. These cows are known as roan cows. (spotty)

Question 51

Incomplete dominance

Answer 51

Incomplete dominance is similar to co-dominance in that both alleles for a given gene are expressed meaning that neither of the two alleles have complete dominance over the other. However, for traits that are incomplete dominant, there is a blending of the two parents’ phenotypes which that visible in the offspring’s phenotype. E.g: red and white flower creating a pink flower

Question 52

Multiple alleles inheritance

Answer 52

there are three alleles that governs the human blood type. These are O, A and B.
• These alleles creates the blood types – A, B, AB and O.
The alleles coding for A and B blood types are co-dominant. This would mean that if the offspring inherits an A allele from one parent the B from another, the offspring will have the blood type AB rather than blood type A or B (which occur if the alleles have a dominant-recessive relationship).
The allele that codes for blood type O is recessive. This means that the offspring must have two alleles that codes for blood type O in order to have blood type of O. This is because if the offspring has an allele that codes for blood type A or B, the allele will override the recessive allele that codes for blood type O.

Question 53

Single nucleotide polymorphisms (SNP)

Answer 53

The term polymorphism refers to the presence of two or more alleles for a gene that exist in at least 1% of the species population.

Question 54

Mis-sense SNP

Answer 54

Substitution of nucleotide occurs. This will lead to an altered codon sequence which specifies a different amino acid.

Question 55

Nonsense SNP

Answer 55

Substitution of nucleotide occurs. This will lead to an altered codon sequence which specifies for a stop codon.

Question 56

Gregor Mendel

Answer 56

What he found was the allele that coded for round pea plants were dominant over the alleles that specified for wrinkled pea plants. This is because he observed that 100% of the offspring in the first generation (F1) were had round peas.
After crossing over heterozygous dominant offsprings in the first generation (RW x RW), he found that 75% of the pea plants were round and 25% of the pea plants were wrinkled in the second generation (F2). This was a 3:1 ratio.
This indicated that wrinkled pea plants was a recessive allele and will only be expressed if the organism’s genotype consists of the two recessive alleles coding for a particular gene. This is because no dominant allele will be present to ‘override’ the recessive allele.

Question 57

Electromagnetic radiation

Answer 57

Electromagnetic radiation is the spectrum of radiation ranging between high-energy gamma rays through low-energy radio waves. The high-energy radiation of gamma rays, x-rays and some ultraviolet rays are capable of breaking and changing chromosomes and causing other mutations by changing DNA.

Question 58

Chemical mutagens

Answer 58

Chemical mutagens are substances that enter cells and counteract with the DNA to cause a range of changes. The changes include base substations, formation of cross links and other changes that impact the structure and function of the DNA. The changes result in mutations. There are many chemical mutagens that primarily target cancer cells because they are rapidly dividing and most susceptible.

Question 59

chemical mutagen example

Answer 59

Benzopyrene is a chemical mutagen and a hydrocarbon present in cigarette smoke that is capable of being inserted between nitrogenous bases, effectively distorting the DNA double helix at the position where benzopyrene is added. This causes wrong nitrogenous bases being complementary paired to template strands during DNA replication.
• This effectively alters the mRNA sequence during protein synthesis which may lead to the specification of a different amino acid sequence in the resultant polypeptide chain.

Question 60

point mutation

Answer 60

Point mutation is when a nitrogenous base is changed at a particular locus on a chromosome. This effectively means that, similar to SNP, point mutation only affects one gene.

Question 61

Chromosomal mutation

Answer 61

Chromosomal mutation affects DNA on a chromosomal level meaning that a section of chromosome is changed rather than a single nitrogenous base. In chromosomal mutation, the section of chromosome that is affected contains more than one gene which means that it affects more than one gene.

Question 62

Effect of somatic mutation on an organism and its offspring

Answer 62

Mutations that occur in the DNA of somatic cells ARE NOT passed onto an organism’s offspring(s) as meiosis and fertilisation does not involve somatic cells. Therefore, the offspring will not inherit the mutation of its parent.

Question 63

Effect of germ-line mutation on organism and its offspring

Answer 63

Mutations that occur in the DNA of germ cells ARE passed onto an organism’s offspring (s) as meiosis involves a germ cell and the DNA contained within the cell.

Question 64

virus’s

Answer 64

Virus is classified as a non-cellular pathogen as they have living and non-living features. They are not made up of cells but rather they have a protein coat containing genetic information in the form of DNA or RNA. This means that they are able to pass on their genetic information via DNA/RNA replication and produce more virus via protein synthesis.

Question 65

Fungi

Answer 65

Although fungi can be unicellular (e.g. yeast) or multicellular (e.g. mushroom), they are all eukaryotes. This means that they have membrane-bound organelles. They also have a rigid cell wall made from chitin. Unlike bacteria and protozoan, they are not motile (non-mobile). They reproduce via spores and spores rely on wind for transportation which germinates upon landing on a surface in a favourable environment such as presence of moisture and preferably cool temperatures. Fungi can either be living on dead tissue (known as saprophyte) or be parasites (thrive on living tissue).

Question 66

Fungi example

Answer 66

Bacteria name: dermatophytosis
Disease: Tinea
Symptoms: darkening of the skin, peeling, red rashes, or scaly patches, blisters, cracking of the skin
Treatment: The treatment for ringworm is an antifungal medication
Vaccine: Ringvac
Prevention: maintain hygiene, keep skin dry, avoid sharing towels, avoid public swimming pools
Mode of transmission = direct contact, skin to skin contact, surfaces e.g. shower floor
Examples of types of tinea include athlete’s foot, ringworm

Question 67

virus example

Answer 67

Virus – Severe Acute Respiratory Syndrome Coronavirus 2
Disease: coronavirus disease (COVID-19)
Symptoms: fever, dry cough, tiredness, conjunctivitis, diarrhea, aches and pains, shortness of breath
Treatment: rest, drink lots of fluids, and eat nutritious foods; self-isolate and visit the doctor.
Prevention: wear mask, sanatise, cough into elbow, maintain safe distance, stay home if feeling unwell.
Vaccine: Moderna, Pfizer
Prevention: quarantine, PPE

Question 68

Bacteria

Answer 68

Bacteria are unicellular, microscopic organisms without membrane-bound organelles. This means that they are prokaryotes and do not have cell membrane. They undergo asexual reproduction via the binary fission process.

Question 69

Bacteria example

Answer 69

Bacteria – Vibrio cholerae
Disease: cholera (a diarrheal infection)
Symptoms: diarrhea, vomiting, leg cramps, dehydration
Treatment: Oral Rehydration Solution (ORS)  mixture of salt and sugar with 1 litre of water and drunk in large amounts. Other treatments include intravenous fluid replacement and antibiotics.
Vaccine: Vaxchora
Prevention: drink and use safe water; wash hands often with safe water; cook food well, peel fruits and vegetables.

Question 70

Prions

Answer 70

Prions are classified as non-cellular pathogen as they do not contain any DNA or RNA

Prions cause neurodegenerative diseases by promoting abnormal folding of proteins in the host’s central nervous system.

Question 71

prions example

Answer 71

Prions – Bovine spongiform encephalopathy (BSE)
Disease: Mad cow disease (also Variant Creutzfeldt-Jakob disease through contaminated food – zoonic disease in humans)
Symptoms: dementia, problems with coordination, psychosis, unresponsiveness, weight loss and drop in milk (for cattle), behavioural changes, trembling.
Treatment: no cure; treatment focuses on keeping patients as comfortable as possible.
Prevention: avoid feeding cattle rendered material from slaughtered animals and to isolate and destroy all infected animals.

Question 72

Macroparasite

Answer 72

This type of eukaryotic pathogen is multicellular and is visible to the human eye. They can be divided into two groups being endoparasites and ectoparasites. Endoparasites lives inside the host organism’s body and obtains food and ectoparasites lives outside the host’s body (e.g. consuming the host’s blood and injecting neurotoxins)

Question 73

Parasite example

Answer 73

Bovicola ovis
Disease: sheep lice
Symptoms: excessive itching and unwarranted wool loss, damaged wool.
Treatment: shearing fleece to remove lice
Prevention: stock-proof fences to prevent sheep from straying and catching lice (known as biosecurity); isolating infected sheep; stock introduced in farm should be quarantined and inspected for lice.

Question 74

diseases on agricultural

Answer 74

Late blight in potatoes
The Irish imported a variety of potato from South America that was eventually grown asexually (via vegetative propagation) to feed their growing population. This made them genetically identical. When the crops became infected by the fungal pathogen, Phytopthora infestans, the entire crop was destroyed due to lack of genetic variation, meaning all potatoes were susceptible to the disease. The potato blight caused the Irish potato famine of the 1840s.

Question 75

disease in animals

Answer 75

Mad Cow Disease
abnormal version of a protein normally found on cell surfaces, called a prion. For reasons still unknown, this protein becomes altered and destroys nervous system tissue – the brain and spinal cord.
Neurological disease cause severe brain and nervous system damage leading to trouble walking and standing and changes in mood; possibly causing increased aggression or nervousness.

Question 76

Design and conduct a practical investigation relating to the microbial testing of water OR food samples

Answer 76

Equipment:
• Food sample (e.g. bread, yogurt and cheese)
• 6x Agar plates
• 1x Incoulating loop
• 1x Bunsen Burner
• Alcohol (e.g. Baby wipes)
• 3x Test tubes
• Pen & Labels
• Sticky tape
Procedure:
Step 1: Sterilise table surfaces using alcohol (e.g. baby wipes)
Step 2: Sterilise your inoculating loop by heating it in the flame of bunsen burner. Also, sterilise three test tubes by heating the ‘mouth’ of the test tubes to restrict/minimise pathogens in the air entering the tubes.
Step 3: Transfer small quantities of three different food sample into three test tubes with 2mL of distilled water and gently mash up the food samples.
Step 4: Dip your sterilised inoculating loop into the food sample in one of your test tube and wipe the food gently on the surface of your agar.
Step 5: Put on the agar plate lid and seal the plate using the sticky tape then label the food type on the lid.
Step 6: Heat your inoculating loop again and repeat Step 4 and Step 5 for your two other types food samples in Test Tubes 2 and 3.
Step 7: Leave 3 sealed agar plates as your control.
Step 8: Observe the number of microbial colonies that are formed in each agar plate and record observations.

Safety:
• Wear gloves to avoid being infection by bacteria.
• When you have sealed the agar plate, do not open it again.
• Take care of using the bunsen burner and hot inoculating loop.
• Wash your hands thoroughly using water and hand-wash solution before leaving the laboratory.

Question 77

Koch’s postulates

Answer 77

1. The pathogen must be associated or responsible for all causes of the disease.
2. The pathogen must be able to be isolated from the affected host, grown in a pure culture and recorded for its characteristics.
3. When the newly cultured pathogen is inserted into a new, healthy (unaffected) host, it must result in the new healthy host in developing the same disease (e.g. same symptoms)
4. The pathogen must be able to be isolated from the newly affected host and shown to be same pathogen (e.g. same characteristics) that was isolated from the original affected host.

Question 78

2 mechanisms of adaptive immunity

Answer 78

• Antibody-mediated immunity (or humoral immunity)  secretion of antibodies into extracellular fluid by B lymphocytes
• Cell-mediated immunity  activation of T lymphocytes

Question 79

natural passively acquired immunity

Answer 79

involves the transfer of antibodies from mother to baby such as diffusion through the placenta. This is passive as the adaptive immune system is not triggered.
• Alternatively, it can also occur after birth where the mother breast feeds the baby where breast milk contains antibodies.

Question 80

passively acquired immunity

Answer 80

immunity involves the injection of antibodies that is produced from one host into another.

Question 81

Antibiotics

Answer 81

Antibiotics are only used to treat bacterial infection whereas antiviral drugs are used to treat viral infection (infections caused by viruses).

Antibiotics affect the metabolic activities of bacteria which does not exist in viruses. Specifically, antibiotics stop cell wall synthesis and protein synthesis occurring in bacteria.
Unlike antibiotics that kills bacteria, antivirals usually don’t kill the virus but rather stop the virus’s development.

Question 82

Homeostasis

Answer 82

Homeostasis is the maintenance of a constant or almost constant internal environment, despite fluctuations in the external environmental.

• Temperature negative feedback loop
• Blood glucose level negative feedback loop

Question 83

Endotherms

Answer 83

Endotherms are organisms uses internal mechanisms to maintain their core body temperature within a narrow range, despite fluctuations in external environment.
• These animals have internal mechanisms allow the generation or production of internal heat energy to regulate their core body temperature. Hence, the term ‘warm-blooded’ animals.

Question 84

Ectotherms

Answer 84

Ectotherms are organisms that do not have internal mechanisms
• These animals DO NOT have internal mechanisms to generate heat and so they must relate on heat from the external environment to regulate their core body temperature. Hence, the term ‘cold-blooded’ animals.
• Indeed, thermoregulation is NOT possible for ectotherms but performed by endotherms.

Question 85

Structural adaptation example

Answer 85

Red Kangaroo – Lives in hot, arid areas of Australia such as deserts & grasslands.
• They have a lot of blood vessels under their forearm and paws. This encourages heat loss via convection to keep their core body temperature within a narrow range, despite the hot ambient surroundings.

Question 86

Physiological adaptation example

Answer 86

Red Kangaroo
The muscle glands can also be activated via thermoregulation in kangaroos to generate heat energy in response to cold temperature stimulus detected by thermoreceptors on skin and in hypothalamus.
Panting is performed by Kangaroo whereby heat energy is loss through ventilation. The process of panting allows water on the tongue and mouth surface to be evaporated as the blood under these surfaces are able to be transferred to the cooler water via conduction.

Question 87

Behavioural adaption example

Answer 87

Red Kangaroos are nocturnal. That is, they sleep during the day and are active during the night to escape the high temperatures of the body to avoid overheating.
They also seek shade to avoid overheating during the day.

Question 88

The nervous system

Answer 88

The nervous system is utilises electrochemical impulses to relay messages regarding to information such as the stimulus detected by receptors and appropriate reaction that is to be performed by effectors to counteract the stimulus and maintain homeostasis.

Question 89

endocrine system

Answer 89

the endocrine system employs hormones which are molecules that interact with specific receptors that are located on or within a specific target cell or tissue to initiate a response from the target cell/tissue. It is this response that allows homeostasis to be achieved and maintained.

Question 90

A stimulus

Answer 90

A stimulus is a change in the internal or external environmental

Question 91

A receptor

Answer 91

A receptor is one or a group of specialised cell that is responsible for detecting stimulus. They are also activated by the stimulus by converting physical feedback into electrochemical pulses or signals.

Question 92

an effector

Answer 92

an effector is an organ in the organism (such as a muscle or gland) that is activated by a neuron to carry out a response to counteract or oppose the stimulus.

Question 93

• The hypothalamus

Answer 93

• The hypothalamus is involved in interpreting the stimulus detected by the receptors in the form of electrochemical signals and decide on an appropriate response to be carried out by relevant effectors to counteract the stimulus in a negative feedback mechanism. This interpretation of signals is performed using large numbers of interneurons in the CNS.
• The hypothalamus is also involved in relaying the appropriate response to be carried out to effectors in the form of electrochemical signals.

Question 94

Anti-Diuretic Hormone (ADH)

Answer 94

ADH (anti-diuretic hormone) is a hormone produced in the hypothalamus, then stored and secreted from the pituitary gland in response to low water levels in the blood
It causes the kidneys to reduce the loss of water in urine.

Osmoregulation: keeping the water content of your blood level

hormone or ADH travels in your blood to your kidney where it will then act on the collecting duct to either tell the collecting duct to reabsorb more water or into the blood at that point or to keep the water in the nephron to be excreted.

Question 95

Mechanisms in plants that allow water balance to be maintained

Answer 95

Hanging leaf orientation: The eucalyptus tree has its leaves hanging in a vertical position so it reduces the surface area in which the leaves are exposed to the sun’s heat at its zenith. This effectively reduces the heat that is absorbed during the hottest time of the day and so it reduces the tree’s risk of dehydration.

Thick, waxy cuticle: Eucalyptus and Banksia plants have thick cuticle that insulates water from excessive sunlight as it reduces the internal temperature. By doing so, the thick cuticle reduces the rate of evaporation.

Question 96

responses of a named endotherm to a decrease in body temperature

Answer 96

Humans are endotherms that in response to a decrease in body temperature may experience vasoconstriction in the region of the skin and increase metabolic heat production by shivering.

Question 97

Outline the role of the nervous system of an endotherm in maintaining homeostasis when its body temperature changes.

Answer 97

The nervous system is responsible for thermoreceptors detecting the change in body temperature and then through the central nervous system activating effector organs such as the muscles that commence shivering or control the constriction or dilation of blood vessels.

Question 98

Pasteur performed an experiment to identify the role of microbes in decay. Justify a conclusion that can be drawn from his results.

Answer 98

A conclusion that can be drawn from the results of Pasteur’s swan-neck flask experiment is that microbes do not spontaneously generate but are a result of direct contact with the air. The conclusion is justified as the flask that was exposed to air became contaminated whereas the one that was sealed from the air by the convoluted shape of the neck of the flask remained uncontaminated.

Question 99

Describe the contribution of Robert Koch to our understanding of disease.

Answer 99

Koch developed rules of procedure (Koch’s postulates) that if followed would demonstrate a direct causal link between the presence of a pathogen and the disease it causes. The steps involved developing pure cultures from infected organisms and infecting heathy organisms with the pure culture and comparing the cultures once the exposed organisms became infected. He identified the bacterial causes of diseases such as anthrax and tuberculosis.

Question 100

Microbial testing of water or food samples

Dependent variable
Control
Variables to be kept constant
Saftey precautions

Answer 100

Dependent variable: The types of colonies that grew from the water or food sample

Control: An agar petri dish on which no sample was grown but which was treated in exactly the same way otherwise; that is, not inoculated

Variables to be kept constant: The same amount of agar medium
The same temperature for each petri dish

Autoclaving of agar plates following incubation and the use of protective clothing, gloves and eyewear

Question 101

Artificial insemination process and outcomes

Answer 101

Collection, storage and transport of semen from male animals with desirable qualities to fertilise a large number of females

Larger numbers of more desirable animals
Global benefits from storage and transport of semen

Question 102

Artificial pollination process and outcomes

Answer 102

Involves the transfer of pollen to stigmas to enable pollination and fertilisation

Improved plant cultivars such as plant hybrids with more vigour and therefore increased productivity beyond that of either parent

Question 103

Compare proteins and polypeptides.

Answer 103

A polypeptide is a chain of specific amino acids joined together by peptide bonds. Secondary and tertiary polypeptide structures result from folding and twisting of the amino- acid chain. A protein consists of at least one polypeptide chain that has a specific conformation. The shape of the combination of polypeptide chains (called quaternary structure) is the result of the interacting forces between the chains. The resultant protein structure is significant for its function.

Question 104

Effect of mutation in gene

Answer 104

A mutation in the AVP gene could result in:
• a substitution of a nitrogenous base in the DNA that could result in a different amino acid in the polypeptide chain that is part of the ADH protein. This may affect the structure and function of the protein or may prematurely terminate the process of polypeptide synthesis

• a deletion or insertion of a DNA base that results in a frameshift mutation that greatly impacts on AVP formation and its ability to function as a hormone.

An AVP mutation could affect the ability of the kidney to reabsorb water and hence the water balance in the blood.

Question 105

Genotype and Phenotype

Answer 105

The term genotype means the genetic make-up. It may refer to the make-up of a pair of specific alleles for a specific characteristic. The term phenotype refers to the manifestation of the genotype as a physical or physiological trait, such as eye colour in humans or blood type. The phenotype results from the expression of the genotype and the interaction with the environment of the organism. (2 marks)

Question 106

Explain how both genotype and phenotype influence the inheritance of genes and natural selection in this population.

Answer 106

Codominance results from the interaction of two different alleles that are both expressed in the heterozygous form. In the case of resistance to the mite the heterozygous mammals will have the advantage of not developing bald patches and having a phenotype resulting in them being better able to resist the cold climate. Heterozygous individuals will pass on to half their offspring the MR allele, thus continuing the allele frequency in the population. Homozygous individuals for the mite-resistant gene are not able to pass on the allele as they have the phenotype that results in them being infertile, tending to reduce the frequency of the allele that conveys resistance to mites. Natural selection will favour the heterozygous phenotype and genotype and maintain a certain level of allele frequency in the population.

Question 107

Process of meiosis

Describe the process that accounts for the changes shown in the model during interphase.

Answer 107

The model shows the chromosomes replicating during interphase. Each chromosome as a result consists of two identical chromatids joined by a centromere. Before this occurs the DNA that is an important component of chromosomes must replicate. This means the double helix unwinds, the strands separate and new strands build using the original strand as a template. The replicated chromosomes contain replicated DNA and hence can carry the genetic material to the next generation.

Question 108

Explain the structure and behaviour of chromosomes in the first division of 5
meiosis. Include detailed reference to the model.

Answer 108

Key events in the first division of meiosis following the formation of identical chromatids include the crossing over of adjacent chromatids from homologous chromosomes. As a result of crossing over, new combinations of alleles are formed on some of the chromatids that eventually separate to become chromosomes. Another process in the first meiosis division is the alignment of the homologous pairs in a random assortment. When the spindles contract, drawing the homologous pairs of chromosomes to opposite poles (and hence different cells), new combinations of chromosomes result. The other key event in the first division is the reduction of the chromosome number from the diploid to the haploid number. This allows gametes to form with the haploid chromosome number, and when they return to the diploid number the potential for genetic variation increases even further.

Question 109

Immunisation definition

Answer 109

Immunisation is the process of using vaccines to protect against illnesses caused by infection. Immunisation means both receiving a vaccine and becoming immune to a disease post-vaccination.

Question 110

Method of DNA analysis

Answer 110

DNA sequencing using the Sanger method. Genetic material is taken from individuals, is isolated and replicated using the Polymerase Chain Reaction.(PCR).
Double stranded DNA is heated to give single strands.
A primer is attached and DNA polymerase is used to build a complementary strand using free nucleotides.
Four types of chain terminating nucleotides are added, each labelled so as to glow a characteristic colour.
In this way a large number of different length strands are produced – identifying each position on the template strand.
Gel electrophoresis is performed and the order in which the strands spread out corresponds to the sequence of bases – shown by colours of terminating nucleotides.
This process is computerised and the whole genome sequenced.

Question 111

how can DNA analysis show patterns in inheritance

Answer 111

DNA analysis would show the degree of relatedness of the different populations. A population with a significantly different range of allele frequencies to a neighbouring population might be considered to have a separate gene pool and hence be a separate species. Previously, biologists had to rely on physical characteristics, and saw the differences between the populations as not great enough to separate them as species. DNA analysis gives a much clearer picture of relatedness.

Question 112

effect of genetic drift on a small population

Answer 112

Genetic drift is the random process by which alleles can be lost from a population. It is particularly important in small populations. This results in a reduction of the gene pool and hence the genetic diversity of a population. When genetic diversity in a species with few individuals gets below a certain level it is very hard for the species to survive as it lacks the genetic variation to adapt to environmental changes or survive diseases.

Question 113

Describe one technique which is used to transfer this genetic material in a named example of a eukaryotic species.

Answer 113

Bt cotton plants contain genes from a bacterium which make them resistant to insect attack. Restriction enzymes are used to remove targeted genes from bacteria. These genes are inserted using a bacterial vector (not the species the genes originally come from, but a species which is able to insert genetic material into host cells). Cells from a cotton seedling are cultured and exposed to the bacterial vector which inserts the genetic material into the cotton cells. This tissue culture is provided with plant hormones to allow it to develop into new seedlings which contain the inserted genes.

Question 114

Explain how mutations of genes which repair DNA, or which control cell division, might cause cancer.

Answer 114

DNA can become damaged due to the action of various mutagens. DNA repair genes produce proteins which are able to arrest gene expression and repair the DNA. Each repair protein is capable of effecting a particular repair – for example one can remove uracil from DNA. Damaged DNA will lead to the gene not functioning correctly – this can lead to a gene becoming an oncogene, one which promotes uncontrolled cell division and tumour development.
OR
Mutations of genes which regulate mitosis can cause uncontrolled cell division which can cause tumours. Eg: the p53 gene’s role is to stop cells dividing if they contain harmful mutation. A mutation in the p53 gene will allow this uncontrolled cell division, leading to tumour formation.