Biology

Question 1

What 3 events occur in all “prophases” of cell division (mitosis and meiosis)?

Answer 1

1. Nuclear membranes break down
2. A spindle made of fibres is formed between centrioles
3. Centrioles separate and move to the poles of the cells

Question 2

What event occurs in all “metaphases”

Question 3

What event occurs in all “metaphases” during cell division (mitosis and meiosis)?

Answer 3

Chromosomes line up at the cell equator, attached to spindle fibres.

Question 4

What 2 events occur in all “anaphases” of cell division (mitosis and meiosis)?

Answer 4

1. Cells constrict at their middles
2. Spindle fibres shorten and pull chromatids/ chromosomes apart

Question 5

What 2 events occur in all “telophases” of cell division (mitosis and meiosis)?

Answer 5

1. Nuclear membranes are reformed
2. Spindle fibres disintegrate

Question 6

Draw, label and annotate the four stages of mitotic cell division.

Answer 6

[See notes.]

Question 7

Draw, label and annotate the first four stages of meiotic cell division.

Answer 7

[See notes.]

Question 8

Draw, label and annotate the final four stages of meiotic cell division.

Answer 8

[See notes.]

Question 9

What 4 events occur in prophase I of meiosis?

Answer 9

1. CHROMATIDS OF HOMOLOGOUS CHROMOSOMES CROSS OVER (break and re-join with each other)
2. The nuclear membrane breaks down
3. A spindle made of fibres is formed between centrioles
4. Centrioles separate and move to the poles of the cell

Question 10

What event occurs during metaphase I of meiosis?

Answer 10

Pairs of homologous chromosomes line up at the cell equator, attached to spindle fibres.

Question 11

What is the name for the point where chromatids of homologous chromosomes cross over during meiotic cell division?

Answer 11

Chiasma

Question 12

What 3 events occur in anaphase I of meiosis?

Answer 12

1. Spindle fibres shorten and pull HOMOLOGOUS CHROMOSOMES apart (Note: The 2 chromatids of each chromosome remain joined)
2. The cell constricts at the middle

Question 13

State 4 differences between mitotic and meiotic CELL DIVISION.

Answer 13

RECALL: Divide 1, divide 2, Pears, Cross Over n

(1) In mitosis, one set of cell division is involved; whereas in meiosis, two sets of cell division are involved.

(2) In mitosis, homologous chromosomes do not pair off; whereas in meiosis homologous chromosomes do pair off.

(3) In mitosis, chromatids do not cross over; whereas in meiosis chromatids do cross over.

(4) In mitosis, cells produced are identical to the parent cell and each other containing the same diploid number (2n) of chromosomes. In meiosis, cells produced are different to the parent cell and each other containing half the number of chromosomes as the parent cell, the haploid number (n).

Question 14

Draw a flow chart of mitosis and meiosis in humans.

Answer 14

[See pg. 242 of textbook.]

Question 15

What are 3 advantages of asexual reproduction?

Answer 15

RECALL: Asexuals Desire Growth Foods

1. Desirable traits such as larger storage organs, larger fruits or resistance to diseases are passed on to offspring since they are all genetically identical.
2. Growth and maturity of plants produced from vegetative propagation are quicker.
3. There is an increased chance of survival of plants produced via asexual reproduction due to a larger food store than in a seed.

Question 16

What are three disadvantages of asexual reproduction?

Answer 16

RECALL: Asexuals Undesire Varied Resources

1. Undesirable traits are passed on, e.g. diseases.
2. Since plants grow up close to their parents, there is competition for resources (nutriets, light and water) due to overcrowding.
3. There is no variation, so the offspring are unable to survive adverse environmental changes

Question 17

What is the importance of mitosis to living organisms?

Answer 17

Mitosis ensures the species chromosome number and the genotype remain the same in all cells of the organism. Mitosis also results in an increased number of cells resulting in growth and repair.

Question 18

Define climate change.

Answer 18

A change in climate or weather patterns due to an increase in greenhouse gas levels in the atmosphere.

Question 19

Define population.

Answer 19

A group of organisms of a single species.

Question 20

Using THREE examples, explain how global warming may lead to an increase in infectious diseases in the Caribbean region.

Answer 20

A rise in sea levels due to global warming contributes to erosion and flooding. The runoff from the floods may lead to the development of stagnant pools of water which act as breeding grounds for mosquitoes which can spread yellow fever, dengue fever and malaria.

Flooding due to global warming can also lead to overflowing drain pipes and sewage systems which can act as breeding grounds for flies which spread cholera and gastroenteritis. Rats also spread leptospirosis.

Increasing temperatures due to global warming may increase the reproductive rates of mosquitoes such as the Aedes Aegypti mosquito increasing disease as mosquitoes are vectors .

Question 21

Explain coral bleaching.

Answer 21

When water is too warm, corals will expel the algae zooxanthellae living in their tissues causing the coral to turn completely white.

Question 22

Explain how global warming happens in 5 stages.

Answer 22

Heat from the Sun reaches the Earth and warms it.

Greenhouse gases form a layer around the earth. These gases are carbon dioxide, methane, ozone, nitrous oxide and fluorinated gases, which are produced from industrial and vehicular pollution.

Heat is radiated back to space.

The layer of greenhouse gases causes some heat to be radiated back, warming the Earth.

This causes Earth to act as a heat trap and there is rising global temperature.

Question 23

What are two trends regarding climate change. Elaborate on both.

Answer 23

Increase in Greenhouse Gases: Gases from industrial and vehicular pollution form a layer around the earth, thus trapping the heat and resulting in global warming.

Rising Global Temperatures: This causes the melting of glaciers, ice caps and ice in the Arctic. As a result, there are rising sea levels and temperatures of seawater, leading to loss of habitats and killing aquatic life, for example, walruses are dying due to melting of ice in the Arctic. This can also result in the extinction of species.

Question 24

Explain ocean acidification.

Answer 24

The increase in carbon dioxide leads to it dissolving in the ocean to form carbonic acid. The pH level of the ocean decreases, leading to ocean acidification. This has a negative impact on marine life, reducing their chances of survival. Organisms such as corals and crustaceans (crabs, shrimps, lobsters) need a certain pH to remove calcium from seawater to build their skeletons. Skeletons grow slower and weaker which leads eventually to destruction of coral reefs. Ocean acidification also poses a threat to ocean wildlife and fish. Hence, less fish is available to humans as food.

Question 25

Define pollution.

Answer 25

Pollution is the introduction of harmful substances into the environment, endangering both ecosystems and human health.

Question 26

What are the three causes of pollution?

Answer 26

Agricultural practices

Industrialization

Improper garbage disposal

Question 27

What are the two sources of pollution in agriculture and their impacts?

Answer 27

Chemical fertilizers: Cause eutrophication, harming aquatic life and harm earthworms, vital for soil fertility and structure.

Insecticides: Harm all insects, including beneficial pollinators, and pose risks to human health. They persist in the environment, poisoning aquatic life when washed into rivers and seas, and concentrating up the food chain, potentially harming top consumers.

Question 28

Due to industrialization, what are two air pollutant sources? What pollutants do they generate, what are the pollutants’ negative impacts, and what are some solutions to conserve and restore the environment?

Answer 28

Due to industrialization, what are two air pollutant sources? What pollutants do they generate, what are the pollutants’ negative impacts, and what are some solutions to conserve and restore the environment?

(1) Construction work/cement factories: Produce dust. Dust settles on buildings and plants, reducing photosynthesis, resulting in less food for animals. Dust also enters rivers, leading to siltation of mangrove swamps and the sea, causing destruction of aquatic life. Dust also causes respiratory diseases such as asthma. Solutions include frequent washing of plant leaves and wearing dust masks.

(2) Burning fuels in vehicles and industry: Produces gaseous smoke and smoke particles. Smoke particles affect human health, causing bronchitis. The smoke contains greenhouse gases such as carbon monoxide, which enter the atmosphere, contributing to global warming. Gases can dissolve in rainwater to produce sulfuric, nitric, or carbonic acid, producing acid rain, which kills plants and hence animals. Solutions include wearing dust masks, utilizing emission control devices and instead of allowing greenhouse gases to enter the air, using them to make fertilizers such as sulfates and nitrates. Cleaner fuel sources such as gasohol or burning garbage for energy to generate electricity can be utilized. Furthermore, altering processes to produce fewer pollutants can help. In addition, alternative forms of energy such as wind, solar, or hydroelectric power can be used.

Question 29

Due to industrialization, what are three water pollutant sources? What pollutants do they generate, what are the pollutants’ negative impacts and what are some solutions to conserve and restore the environment?

Answer 29

Aluminium plants: Produce chemical waste and caustic sludge. These pollutants are released into ponds and rivers, killing aquatic life such as fish. Solutions include treating effluence, disposing of waste in proper areas, and passing laws for industries to change chemical waste into less harmful substances.

Desalination plants and electric power stations: Produce “industrial heat.” This hot water enters aquatic habitats. High water temperatures can lead to coral bleaching, destroying coral reefs. Less oxygen dissolves in hot water; therefore, less oxygen is available for the respiration of animals. The solution to this is cooling water and directing it to ponds.

Drilling in sea and on land: Produces oil spills. These kill plants and animals. Solutions include using detergent, however, this is also a pollutant, or the use of microbial action.

Question 30

Improper garbage disposal is a form of pollution. Name three forms of garbage disposal, their negative impact on man and the environment, and measures to conserve and restore the environment.

Answer 30

Burning garbage: This causes toxic gases to enter the atmosphere, increasing the amount of greenhouse gases in the atmosphere. Solutions include avoiding burning garbage, burning biodegradable garbage in incinerators, and using the energy produced to generate electricity.

Dumping garbage on empty lots or in rivers: This is unsightly and foul-smelling. It also creates a breeding ground for pests such as rats and roaches, which can be vectors of disease. This causes pollution of soil and water. Furthermore, non-biodegradable materials such as plastics enter aquatic habitats, killing aquatic life. Solutions include educating the public to reduce, reuse, and recycle. Biodegradable waste should be used to make compost heaps, and food processing waste can be used to make organic fertilizers.

Landfill sites: If garbage is not treated and buried quickly, this can be a breeding ground for pests, which can act as vectors of disease. It also creates a bad odor, which can have a negative health impact on the residents living near the landfill. Solutions include using methane gas produced from landfills to generate electricity.

Question 31

What are three negative impacts of pollution on eco-tourism?

Answer 31

1. Destruction of Tourist Attractions (coral reefs, mangroves, beaches)
2. Dust and Smoke in the Air
3. Unsightly, foul-smelling garbage present

Question 32

What 3 implications of pollution of marine and wetland environments?

Answer 32

1. Loss of income for economy and aesthetics
2. Destruction of habitats and aquatic life
3. Less seafood for humans

Question 33

What are the four measures to conserve fossil fuels? Elaborate.

Answer 33

Energy conservation: Educate the public through schools and mass media about the need to conserve energy by using less electricity or considering alternative sources of energy.

Use of alternative sources of energy: For example, solar, wind, burning garbage, and hydroelectric power. Vehicles can use electricity or gasohol (a mixture of ethanol and gasoline).

Biogas: Can be used for cooking as an alternative to fossil fuels.

Utilising methane produced from fossil fuel use: Instead of methane entering the atmosphere, it can be used as an energy source to generate electricity.

Question 34

What are 3 measures to conserve minerals?

Answer 34

Less minerals should be used due to the limited supply.

Governments can impose a mining tax to disincentivize the exploitation of minerals.

Metals can be recycled and reused.

Question 35

For what 7 potential reasons are trees removed by humans? What 4 effects does the removal of trees have on the environment?

Answer 35

Trees are removed for the following reasons: paper, timber, housing, agriculture, roads, industry, and medicine.

The effects of the removal of trees are:

Reduces the amount of food available for animals since plants photosynthesize and manufacture food.

There is an increase in the level of carbon dioxide in the air as plants use carbon dioxide during photosynthesis.

Habitats are destroyed which can lead to the depletion or extinction of species.

Erosion of topsoil.

Question 36

What are 5 effects the erosion of topsoil can have? What are three measures to conserve forests and soil?

Answer 36

Erosion of topsoil leads to loss of soil fertility, silting of the waters, floods, landslides, and loss of livestock and crops. This can lead to the loss of income for farmers, resulting in high economic costs.

Measures to conserve forests and soil include:

Reforestation programs.

Designating certain areas as nature reserves to protect trees and wildlife.

Implementation of soil conservation plans.

Question 37

What are 4 impacts of human activities on the marine environment? Elaborate on them.

Answer 37

Overfishing: Humans fish for seafood, leading to the depletion or extinction of certain species.

Overfertilization: Excessive fertilizer use can pollute the sea and cause eutrophication, resulting in the overgrowth of marine algae.

Destruction of coral reefs: Eutrophication reduces light to coralline green algae zooxanthellae, leading to the death of coral polyps.

Oil spills: Oil spills from offshore drilling and tankers can kill marine life.

Question 38

Draw a diagram to illustrate the carbon cycle.

Answer 38

[Refer to textbook page 30.]

Question 39

What are the seven minerals that are important for plant nutrition? State the importance of each to a plant and the deficiency signs.

Answer 39

RECALL: Never Mind I Play Cricket Properly Sancho

[Refer to textbook page 77.]

Question 40

State three reasons why decomposers are important in an ecosystem.

Answer 40

Reduces the buildup of waste.

Recycles nutrients.

Aids in the flow of energy in the ecosystem.

Question 41

Suggest two reasons why carbon dioxide is described as a greenhouse gas.

Answer 41

Carbon dioxide absorbs radiant energy.

Carbon dioxide radiates heat to Earth.

Question 42

What are three differences between decomposers and plants in terms of nutrition?

Answer 42

Decomposers require no light for their nutrition, depend on other organisms for food to break down organic molecules into simpler molecules. Plants, on the other hand, require light for their nutrition, are autotrophic meaning they make their own food, and use simple molecules to make organic molecules.

Question 43

In terms of THE CARBON CYCLE, suggest TWO strategies to reduce the amount of carbon dioxide in the atmosphere.

Answer 43

Plant more trees.

Reduce combustion.

Question 44

Explain the transpiration stream in five steps.

Answer 44

The concentration of water vapour in the air is less than the concentration of water vapour in the intercellular airspace, so it diffuses out of the airspace.

Water evaporates from cell surfaces into the intracellular airspace.

Water is drawn from mesophyll cells via osmosis.

Water from xylem vessels replaces lost water in mesophyll cells via osmosis. This creates a transpiration pull.

Water moves up xylem as a continuous column due to capillarity, root pressure, and transpiration.

Question 45

What five environmental factors affect transpiration?

Answer 45

Light intensity: During daytime when photosynthesis is taking place, stomata are open to allow carbon dioxide to enter. As light intensity increases, the rate of transpiration increases because the rate of diffusion of water vapour through the pores increases. When the light intensity decreases, the transpiration rate decreases because the pores begin to close.

Temperature: There is faster evaporation of water at higher temperatures leading to a higher transpiration rate. At lower temperatures, the transpiration rate will decrease due to the slower evaporation of water.

Humidity: High humidity means there is a greater amount of water vapour in the air and it cannot hold much more. Therefore, the transpiration rate will be low in times of high humidity. In low humidity (dry air), the transpiration rate increases.

Air movement: Windy conditions will increase the transpiration rate because the water vapour will be removed quickly from the stoma. In still air, the transpiration rate will decrease because the air space is saturated with water vapour.

Water availability: Stomata close when the guard cells become flaccid in times of water shortage, and the transpiration rate will slow down.

Question 46

Answer Q1 (a) (i) and (ii) of May/June P2 2019.

Answer 46

(i)

Without any weight on the beam balance, move all of the counter masses to the zero marks.

Turn the zero adjustment knob until the pointer aligns with the zero mark.

Place the plant on the beam balance and record the initial mass.

Place the plant by the window.

Measure and record the mass of the plant after an hour has elapsed.

Repeat steps 4 and 5 for a total time of 12 hours.

Plot a graph of mass of the potted plant versus the time of day.

(ii)

Use a fresh and healthy plant OR Ensure that the polythene bag is properly sealed.

Question 47

What are two reasons why a plant may need proteins?

Answer 47

To make enzymes.

To make hormones.

Question 48

Draw, label, and annotate a rough sketch of a vertical section of a leaf.

Answer 48

[Refer to notes.]

Question 49

Draw, label and annotate the structure of an alveolus cell.

Answer 49

[See notes.]