Biology Paper 2 Predictions 2024

What is a receptor?

What is a receptor?

A cell that detects a stimulus (a change in conditions)

What is the purpose of the coordination centre?

Process information and organise a response

What is the purpose of the effector?

A muscle or gland that carries out a response to bring conditions back to optimal level

What is the purpose of the frontal cortex?

Outer wrinkly part that controls language, memory and consciousness

What is the purpose of the cerebellum?

Back, right spongey looking thing - controls muscle coordination

What is the purpose of the medulla?

Pink bumpy thing that is next to the spinal coord - controls unconscious activities

How can the brain be studied?

• Look at patients with brain damage - check which parts of the brain are damaged and see how that affects the patient

• MRI Scans - tell a person to carry out tasks and see which parts of the brain are active

• Electrical stimulation - use an electrode to stimulate parts of the brain and see what happens

What is the purpose of the kidneys?

To produce urine by removing waste products from the blood

What is selective reabsorption?

The process in which useful substances are reabsorbed from the kidneys

What is the hormone that controls water levels in the body? Where is it secreted from?

ADH, from the pituitary gland

What happens if water levels are low?

• More ADH is secreted

• More water is reabsorbed from kidneys by selective reabsorption

• Concentration of urine increases

What happens if water levels are too high?

• Less ADH is secreted

• Less water is reabsorbed from kidneys by selective reabsorption

• Concentration of urine decreases

How does proteins get converted into urea?

• Body can not store proteins so they have to be converted into carbs and fats

• This process releases ammonia which is toxic to the body

• Ammonia is converted into urea in the liver

What happens if ion levels are too low?

More ions are reabsorbed from the kidneys by selective reabsorption

What substances do the kidneys filter from the blood?

• Urea

• Ions

• Water

Process of dialysis

• Blood flows through the dialysis machine

• Waste products are filtered out through the partially permeable membrane

• Dialysis fluid contains same concentration of glucose and ions as the blood, so these substances are not lost

What are the pros and cons of dialysis?

Pros: allow you to buy time for a kidney transplant

Cons: Time consuming (has to be done 3-4 times a week), expensive, can cause blood clots and infection, unpleasant

What are the pros and cons of kidney transplants?

Pros: effectively treat kidney failure, cheaper in the long run than dialysis

Cons: Can be rejected by the immune system, immunosuppresants have to be taken which leave you compromised

What are the stages of the menstrual cycle:

Day 1-4: uterus lining breaks down

Day 4-14: uterus lining is built up

Day 14: ovulation, mature egg is released from ovaries

Day 14-28: uterus lining is maintained to allow the egg to become fertilised

What are the hormones used in the menstrual cycle?

1) FSH - causes egg to mature, stimulates release of oestrogen

2) Oestrogen - builds up lining of uterus, stimulates release of LH, inhibits release of FSH

3) LH - causes egg to be released from ovaries

4) Progesterone - maintains lining of the uterus, inhibits release of FSH and LH

How does oestrogen control fertility?

Inhibits release of FSH, which prevents egg from maturing

How does progesterone control fertility?

Builds up thick mucus on uterus lining, blocks sperm from passing so egg does not become fertilised

What is the process of thermoregulation?

• Thermal receptors on skin detect temperature change

• Thermoregulation centre in the brain coordinates a response

• Muscles and glands carry out response to bring body temperature to optimum levels (37 degrees celcius)

What happens if you are too hot?

• You start to sweat, cools you down when it evaporates

• Vasodilation, blood vessels swell to the surface of the skin which increases rate at which heat is lost (energy is transferred to surroundings)

What happens if you are too cold?

• You start to shiver, repeated muscle contraction transfers energy from respiration to warm you up

• Hairs stand to trap insulating layer of air

• Vasoconstriction, blood vessels constrict to minimise heat loss

How do auxins work in a phototropism?

Auxins move towards the side of the plant which is exposed to shade, causing the plant to grow in the direction of the light

How do auxins work in a gravitropism?

• Auxins move towards the lower side of the plant

• In shoots, auxins promote growth so the shoot grows upwards

• In roots, auxins inhibit growth so the root grows downwards

What are the uses of auxins?

• Grow plants from cuttings

• Grow cells in tissue culture

• Kill weeds

What are the uses of gibbirelines?

• Increases yield of fruit

• Induces flowering

• Allows you to grow plants when they are dormant

What are the uses of ethenes?

• Release an enzyme which causes plants to ripen

What is DNA?

The chemical which contains coded information that instructs what characteristics you inherit, found in the nucleus in chromosomes

What monomers make up DNA?

Nucleotides

What is a gene?

A small section of DNA on a chromosome

• Instructs the cell to make certain amino acids, and arrange them in a certain way to make proteins

What is a genome?

All of the genetic information of an organism

Why is the genome important?

• Allows us to see which genes are linked to hereditary diseases

• Increases understanding of hereditary diseases, which can lead to treatments

• Allows us to see the migration of populations

What is sexual reproduction?

The process in which a male and female gamete fuse and combine genetic information to produce an offspring that is genetically different

What is the male and female gamete in human reproduction?

Male: sperm - 23 chromosomes

Female: egg - 23 chromosomes

What is the male and female gamete in plant reproduction?

Male: pollen

Female: egg cells

What is asexual reproduction?

The process in which a cell divides by mitosis to produce two genetically identical offspring

What are the advantages of sexual reproduction?

• More variation (survival of the fittest)

What are the advantages of asexual reproduction?

• Happens faster

• Uses less energy

• Only needs one parent

What pair of chromosomes decide if you are female?

XX

What pair of chromosomes decide if you are male?

XY

What is a genotype?

The combination of alleles in an organism

What is a phenotype?

The characteristics of an organism

What conclusions did Mendel find?

• Characteristics are decided by hereditary units

• Hereditary units are passed down by parents

• Hereditary units can be recessive or dominant

How did Mendel find his conclusion?

1st crossing: crossed a dwarf and tall pea plant together, four tall pea offsprings produced

2nd crossing: crossed two of the two tall offsprings together, 3 tall pea plants produced, one dwarf pea plant produced

What is the theory of evolution?

All living organisms descend from simple organisms that have been developing for over three billion years

Darwin’s theory of evolution

• Noticed that different organisms in the same species had different phenotypic variation

• Organisms with the desired characteristics would be able to survive and reproduce as they would be able to gather resources more effectively

• Organisms without desired characteristic would not be able to survive and reproduce

• Desired characteristic will be carried down to further generations

Why was Darwin’s theory of evolution controversial?

• Went against religious teachings

• Darwin could not explain his theory as mutations had not been discovered

• There was not enough evidence as there were no studies to show that organisms change over time

What was Lamarck’s theory of evolution?

• Organism changes in its lifetime due to environmental factors

• These changes would be passed down to offspring

Theory was disproven as experiments showed it was false

What is genetic engineering?

The process in which you transfer a gene responsible for a desired characteristic from one organism to another

Process of genetic engineering

• Useful gene is isolated from genome using enzymes and transferred to a vector

• Vector is exposed to target organism and gene is inserted

What are the pros of genetically modified crops?

• Higher yield

• Nutrients can be added to foods

What are the cons of genetically modified crops?

• Long term effects are unknown

• Transplanted genes can enter the environment and produce herbicide resistant weeds

• Reduce biodiversity

What is classification?

The process in which organisms are split into groups

What is the order of groups in the Linnaen system?

Kingdom, phylum, class, order, family, genus, species

Why was the three-domain system made?

Advancements in technology allowed us to find that organisms which we thought were related were not

What are the three domains?

• Archaea: prokaryotic cells that are not bacteria

• Bacteria

• Eukaryota: eukaryotes

What is the order of groups in the three domain system?

Domain, kingdom, phylum, class, order, family, genus, species

What is the binomial system?

Every organism is given a two part Latin name

First part: genus

Second part: species

What is a biotic factor?

A living factor that affects the environment

What is an abiotic factor?

A non-living factor that affects the environment

The Water Cycle

1) Water in land and sea evaporates, water in plants evaporate in transpiration - this produces water vapour

2) Water vapour rises and condenses to form clouds

3) Water from clouds fall as precipitation

4) Water drains into sea - cycle is repeated

Decay Cycle

• All living things are made up of complex compounds which get passed up the food chain

• Complex compounds are returned to environment as waste products

• Waste products are decayed/digested by microorganisms

• Elements needed to make the complex compounds for plants are returned into the soil - cycle continues

Carbon Cycle

• Carbon dioxide is removed from environment by plants in photosynthesis

• Carbon dioxide is released when plants respire

• Animals eat plants, carbon in plants stored in protein and fat - this moves down the food chain

• Carbon dioxide is released when animals respire

• Animals produce waste

• Animal waste, animal and plant remains are broken down by microorganisms and detritus feeders

• Microorganisms and detritus feeders respire and release carbon dioxide

What is compost?

Decomposed organic matter that is used as a plant fertilizer

What factors affect rate of decay?

• Temperature

• Oxygen levels

• Water levels

• Number of decay organisms available

What is biodiversity?

The variety of organisms in a given area

How do humans decrease biodiversity?

• Increase global warming levels which destory habitats

• Deforestation

• Producing waste

How do humans try to increase biodiversity?

• Set up breeding campaigns so that endangered species can reproduce

• Protect and regenerate rare habitats

• Introduce hedgegrows to increase variety of plants

• Reducing amount of waste going to landfill

• Government schemes to decrease deforestation

What is the 1st trophic level?

Producers - plants

What is the 2nd trophic level?

Primary consumers - herbivores

What is the 3rd trophic level?

Secondary consumers - carnivores

What is the 4th trophic level?

Tertiary consumers - carnivores that eat other carnivores

What is the equation for efficiency of biomass transfer?

(transfer to next level / previous level) x100

How is bacteria used to produce human insulin?

• Get a plasmid and human chromosome

• Take out insulin gene from human chromosome using a restriction enzyme - produces a sticky side

• Use restriction enzyme on the plasmid to produce a sticky side

• Use ligase enzyme on the insulin gene and plasmid, the sticky sides will bind

• Insert the binded gene into a bacterium