Biology Paper 2

What is a stimulus?

A change in the environment that causes a response.

What is a receptor?

A specialised cell that detects a stimulus.

What is an effector?

A muscle or gland that produces a response.

What is the central nervous system?

The brain and spinal cord.

What is the peripheral nervous system?

All neurones outside the brain and spinal cord.

Describe the reflex arc.

Stimulus detected by receptor, sensory neurone carries impulse to spinal cord, relay neurone passes impulse, motor neurone carries impulse to effector, effector produces response, brain informed after.

Why are reflex actions fast?

They bypass the brain and are processed in the spinal cord.

What is a voluntary action?

A conscious action controlled by the brain.

What is a reflex action?

A rapid, automatic response to a stimulus.

Function of the cerebrum.

Controls conscious thought, memory, intelligence and voluntary actions.

Function of the cerebellum.

Controls balance, posture and coordination.

Function of the medulla.

Controls unconscious actions such as breathing and heart rate.

What is a synapse?

A gap between two neurones.

How does a synapse work?

Electrical impulse causes neurotransmitter release which diffuses across the synapse and triggers a new electrical impulse.

Why are synapses one directional?

Neurotransmitters are released from only one neurone.

What is a hormone?

A chemical messenger released into the bloodstream.

What is an endocrine gland?

A gland that releases hormones directly into the blood.

What is the role of the pancreas?

Releases insulin and glucagon to control blood glucose.

How does insulin work?

Released when blood glucose is high, causes glucose to be converted to glycogen in the liver, lowering blood glucose.

How does glucagon work?

Released when blood glucose is low, causes glycogen to be converted to glucose, raising blood glucose.

What is negative feedback?

A control mechanism that reverses changes to maintain normal conditions.

Compare nervous and hormonal control.

Nervous control is fast and short lasting using electrical impulses, hormonal control is slower and long lasting using chemical messengers.

What is FSH?

A hormone that stimulates egg maturation and oestrogen release.

What is the role of oestrogen?

Rebuilds the uterus lining and inhibits FSH.

What is the role of LH?

Triggers ovulation.

What is the role of progesterone?

Maintains the uterus lining.

Why does menstruation occur?

A fall in progesterone causes the uterus lining to break down.

Define homeostasis.

Regulation of internal conditions to maintain optimum enzyme activity.

What is thermoregulation?

The control of body temperature.

What happens when the body is too hot?

Sweating and vasodilation increase heat loss.

What happens when the body is too cold?

Shivering and vasoconstriction reduce heat loss.

What is vasodilation?

Widening of blood vessels to increase heat loss.

What is vasoconstriction?

Narrowing of blood vessels to reduce heat loss.

What is osmoregulation?

Control of water balance in the body.

What is ADH?

A hormone that controls water reabsorption in the kidneys.

Where is ADH released from?

The pituitary gland.

What is the role of ADH?

Increases water reabsorption in kidney tubules, producing concentrated urine.

How do the kidneys work?

Blood is filtered, useful substances are reabsorbed, urea is removed, urine is produced.

What is dialysis?

A treatment that replaces some kidney functions by removing waste from blood.

One advantage of dialysis.

Available immediately.

One disadvantage of dialysis.

Time consuming and restrictive.

One advantage of a kidney transplant.

Improves quality of life.

One disadvantage of a kidney transplant.

Risk of organ rejection.

What is fertilisation?

The fusion of male and female gametes.

What is a gamete?

A sex cell.

What is the male gamete?

Sperm.

What is the female gamete?

Egg or ovum.

What is sexual reproduction?

Reproduction involving two parents and genetic variation.

What is asexual reproduction?

Reproduction involving one parent and no genetic variation.

One advantage of sexual reproduction.

Produces genetic variation.

One advantage of asexual reproduction.

Faster population growth.

Describe IVF treatment.

Hormones stimulate egg production, eggs collected and fertilised in a lab, embryos inserted into the uterus.

What is the function of the placenta?

Exchanges oxygen, nutrients and wastes between mother and fetus without mixing blood.

What hormone causes male puberty changes?

Testosterone.

What hormone causes female puberty changes?

Oestrogen.

What is variation?

Differences between individuals of the same species.

What causes variation?

Genetic, environmental or a combination of both.

What is a gene?

A section of DNA that codes for a protein.

What is an allele?

A different version of a gene.

What is a mutation?

A change in the DNA sequence.

Describe natural selection.

Variation exists, organisms compete, those with advantageous traits survive and reproduce, passing on alleles, population evolves.

Explain antibiotic resistance.

Mutation creates resistance, antibiotics kill non resistant bacteria, resistant survive and reproduce, resistance spreads.

What is selective breeding?

Humans selecting organisms with desirable traits to breed.

One risk of selective breeding.

Inbreeding leading to genetic defects.

What is the independent variable?

The variable that is changed.

What is the dependent variable?

The variable that is measured.

What is a control variable?

A variable kept the same.

What is reliability?

How consistent results are.

How can reliability be improved?

Repeating experiments and calculating a mean.

What is accuracy?

How close a result is to the true value.

What is an anomaly?

A result that does not fit the pattern.

What is mitosis?

Cell division that produces two genetically identical diploid daughter cells.

What is meiosis?

Cell division that produces four genetically different haploid gametes.

How many divisions occur in mitosis?

One division.

How many divisions occur in meiosis?

Two divisions.

How many daughter cells are produced in mitosis?

Two daughter cells.

How many daughter cells are produced in meiosis?

Four daughter cells.

What is the chromosome number after mitosis?

Diploid, same as the parent cell.

What is the chromosome number after meiosis?

Haploid, half the parent cell.

Are daughter cells genetically identical in mitosis?

Yes.

Are daughter cells genetically identical in meiosis?

No, they show genetic variation.

What is the role of mitosis?

Growth, repair and asexual reproduction.

What is the role of meiosis?

Production of gametes and genetic variation.

State two differences between mitosis and meiosis.

Mitosis produces two identical diploid cells in one division, meiosis produces four different haploid cells in two divisions.

What causes the pupil to change size?

Changes in light intensity entering the eye.

How does the pupil change size?

In bright light circular muscles contract and radial muscles relax making the pupil smaller, in dim light circular muscles relax and radial muscles contract making the pupil larger.

What gland reduces water loss along with the kidney?

The pituitary gland.

Why is a kidney transplant better than dialysis?

A transplant allows a normal lifestyle without frequent treatment and has better long term outcomes.

How does the eye focus on a near object?

Ciliary muscles contract, suspensory ligaments loosen, lens becomes thicker and more curved.

How does the eye focus on a distant object?

Ciliary muscles relax, suspensory ligaments tighten, lens becomes thinner.

How do spectacle lenses correct long sightedness?

A convex lens bends light rays inward so they focus correctly on the retina.

How does auxin cause different growth in two seeds?

Auxin accumulates on the shaded side causing cells to elongate more so the shoot bends.

Why do two seeds grow differently if auxin is unevenly distributed?

Cells with more auxin elongate faster causing unequal growth.

Why does a person with type 2 diabetes have high insulin levels?

The body becomes less responsive to insulin so more is produced to try to lower blood glucose.

How do insulin and glucagon control blood glucose?

Insulin lowers blood glucose by converting glucose to glycogen, glucagon raises blood glucose by converting glycogen to glucose.

Describe the process of natural selection.

Variation exists, organisms compete, those with advantageous traits survive and reproduce, traits are inherited, population evolves.

How do genes control protein production?

Genes code for amino acid sequences which are assembled to make proteins.

What is a Punnett square used for?

To predict the probability of offspring genotypes.

How do you complete a Punnett square?

Write parent alleles on each side, combine alleles in boxes, calculate genotype ratios.

How does the body prevent pathogens entering?

Skin acts as a barrier, mucus traps pathogens, cilia move mucus out of airways.