Bio Paper 2

What is an abiotic factor?

A non-living factor that affects organisms, such as temperature, light intensity or soil pH.

What is a biotic factor?

A living factor that affects organisms, such as predators, competitors or food availability.

What is evaporation?

The process where liquid water changes into water vapour.

What is precipitation?

Water falling from clouds as rain, snow, sleet or hail.

What is a population?

All members of one species living in a particular habitat.

What is a community?

All the populations of different species living in a habitat.

What is a habitat?

The place where an organism lives.

What is an ecosystem?

A community of organisms interacting with each other and their physical environment.

What is a producer?

An organism, usually a plant, that makes its own food through photosynthesis.

What is a primary consumer?

An organism that eats producers.

What is a secondary consumer?

An organism that eats primary consumers.

What is a trophic level?

The feeding position an organism occupies in a food chain.

Why do most food chains have a maximum of five trophic levels?

Energy is lost at each trophic level, leaving less energy available to support organisms higher up.

How is energy lost between trophic levels?

Through respiration, movement, heat, waste and uneaten material.

How is energy transferred between organisms?

Through feeding.

What is biomass?

The total mass of living biological material in an organism or group of organisms.

How is biomass lost from a food web?

Through respiration and egestion.

What is a predator?

An organism that hunts and eats another organism.

What is prey?

An organism that is hunted and eaten by a predator.

What is competition?

When organisms compete for limited resources such as food, water, light or territory.

What is parasitism?

A relationship where one organism benefits while the host is harmed.

What is mutualism?

A relationship where both organisms benefit.

What is biological control?

Using living organisms to control pest populations.

What is biodiversity?

The variety of different species living in an ecosystem.

What is capture-recapture?

A method of estimating population size by capturing, marking, releasing and recapturing organisms.

What is a quadrat used for?

Sampling the abundance or distribution of organisms in an area.

How can quadrats be used to estimate plant populations?

Place quadrats randomly, count organisms and calculate an average per unit area.

Why should quadrats be placed randomly?

To reduce sampling bias and obtain representative results.

How can scientists improve the accuracy of population estimates?

Use more samples, sample randomly and cover a larger area.

How is percentage area sampled calculated?

(Area sampled ÷ total area) × 100.

What is the difference between continuous and discontinuous variation?

Continuous variation has a range of values; discontinuous variation has distinct categories.

Give an example of discontinuous variation.

Sex.

What is sexual reproduction?

Reproduction involving the fusion of male and female gametes.

What is a characteristic of sexual reproduction?

Offspring show genetic variation.

What is asexual reproduction?

Reproduction involving one parent without fusion of gametes.

What is a mutation?

A random change in DNA that can create new alleles.

What is an allele?

An alternative version of a gene.

What is a genotype?

The alleles an organism possesses.

What is a phenotype?

The observable characteristics of an organism.

What is a dominant allele?

An allele expressed in the phenotype if at least one copy is present.

What is a recessive allele?

An allele expressed only when two copies are present.

What is a homozygous genotype?

Two identical alleles for a gene.

What is a heterozygous genotype?

Two different alleles for a gene.

What genotype causes cystic fibrosis if f is recessive?

ff.

What is the genotype of a carrier of cystic fibrosis?

Ff.

What percentage of offspring have cystic fibrosis from Ff × Ff?

25%.

What is the genotype ratio from Ff × Ff?

1 FF : 2 Ff : 1 ff.

What is the phenotype ratio from Ff × Ff?

3 unaffected : 1 affected.

Which sex chromosomes are found in human egg cells?

One X chromosome.

Which sperm chromosome produces a male baby?

A Y chromosome fertilising an X chromosome egg.

How many chromosomes are in a gamete if a body cell has 16 chromosomes?

8 chromosomes.

What is selective breeding?

Humans choosing organisms with desirable characteristics to reproduce.

What are the steps of selective breeding?

Choose desired features, select parents, allow them to mate, select offspring with desired features and repeat over generations.

Why do farmers use selective breeding?

To produce organisms with desirable characteristics, such as higher milk yields.

How do farmers choose animals for selective breeding?

They select animals with desirable characteristics to reproduce.

What are disadvantages of selective breeding?

It reduces genetic variation and can increase the chance of inherited genetic disorders.

What is genetic modification?

Changing an organism's DNA by inserting a gene to produce a desired characteristic.

Give two characteristics that crops could be genetically modified for.

Pest resistance and disease resistance.

Give another characteristic crops could be genetically modified for.

Higher nutritional value or increased yield.

What is natural selection?

The process where organisms with advantageous inherited characteristics survive and reproduce more successfully.

How does natural selection cause pesticide resistance?

Resistant insects survive pesticide use, reproduce and pass resistance alleles to offspring. Resistance becomes more common over generations.

How does natural selection cause antibiotic resistance?

Resistant bacteria survive antibiotic treatment, reproduce and pass resistance genes to offspring.

Why does pesticide resistance matter to farmers?

Pesticides become less effective because resistant insects survive and reproduce.

Why can warfarin resistance increase in rat populations?

Resistant rats survive poisoning, reproduce and pass the resistance allele to their offspring.

What is the expected genotype ratio from Rr × Rr?

1 RR : 2 Rr : 1 rr.

What is the expected phenotype ratio from Rr × Rr if R is dominant?

3 resistant : 1 non-resistant.

What is a stem cell?

An unspecialised cell that can divide and differentiate into specialised cells.

Why are stem cells useful in medicine?

They can differentiate into different types of cell to replace damaged tissues.

What is an ethical issue with embryonic stem cells?

Embryos may be destroyed during the process.

What is molecular phylogenetics?

Classifying organisms by comparing their DNA sequences.

What does evolution mean?

The gradual change in inherited characteristics of populations over generations.

What is the purpose of vaccination?

To stimulate an immune response and provide protection against a pathogen.

What do vaccines contain?

Dead, weakened or inactive forms of a pathogen, or its antigens.

How do vaccines protect the body?

They stimulate white blood cells to produce antibodies and memory cells.

What are antigens?

Chemical markers on the surface of pathogens or foreign cells.

Which cells produce antibodies?

White blood cells, particularly lymphocytes.

What do antibodies do?

They bind to specific antigens and help destroy pathogens.

What is the function of platelets?

They help blood clot and prevent excessive blood loss.

What is the function of mucus in the airways?

It traps pathogens and particles.

How does stomach acid protect the body?

It kills many pathogens entering through food.

What is a communicable disease?

A disease that can spread between organisms.

What is a non-communicable disease?

A disease that cannot spread between organisms.

What pathogen causes tuberculosis?

Bacteria.

What pathogen causes AIDS?

HIV, a virus.

What pathogen causes tobacco mosaic disease?

A virus.

What pathogen causes crown gall disease?

Bacteria.

What pathogen causes barley powdery mildew?

A fungus.

What causes type 2 diabetes?

A combination of genetic and lifestyle factors, not a pathogen.

What is HIV?

A virus that attacks the immune system.

How does HIV increase the risk of tuberculosis?

It weakens the immune system, making the person more vulnerable to infections.

Why don't antibiotics work against viruses?

Viruses reproduce inside host cells and lack the bacterial structures targeted by antibiotics.

Why should antibiotics only be prescribed for bacterial infections?

They do not kill viruses, and unnecessary use increases antibiotic resistance.

Why might doctors wait before prescribing antibiotics for sinusitis?

Viral sinusitis often improves naturally, while bacterial symptoms may persist.

What is an antibody?

A protein produced by white blood cells that binds to a specific antigen.

What is a placebo?

A treatment that looks like the real treatment but contains no active ingredient.

Why is a placebo group used in medical trials?

To provide a control for comparison and identify the treatment's actual effect.

Why should medical trials be repeated by other researchers?

To check reproducibility and increase confidence in the results.

Why are treatments tested on animals before humans?

To investigate safety and effectiveness before human trials.

What is a risk factor for cardiovascular disease?

A diet high in saturated fat.

Can someone be free from disease but not be healthy?

Yes. Health also includes mental and social wellbeing.