AQA Combined Science Biology Paper 2

What is homeostasis?

The regulation of the internal conditions in a cell or organism to maintain optimum conditions for function in response to internal and external changes

What key three factors does homeostasis in human control?

Blood glucose concentration, body temperature, water levels

What does the nervous system do in humans?

Enable humans to react to their surroundings and to coordinate their behaviour

What is the Central Nervous System?

The brain and spinal cord

What does the Central Nervous System do?

Coordinates the response of effectors which may be muscles or gland secreting hormones

What is the Central Nervous System sequence?

Stimulus --> Receptor --> Coordinator --> Effector --> Response

What is the endocrine system?

A system composed of glands which secret chemicals called hormones directly into the bloodstream

What is the pituitary gland?

The 'master gland' in the brain which secretes hormones into the blood in response to body conditions

What does the pancreas do?

Monitor and control blood glucose concentration

What happens when the blood glucose concentration is too high?

The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells

H What happens when the blood glucose concentration is too low?

The pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and release into the blood

What is glucose converted to in liver and muscle cells?

Glycogen

What is Type 1 diabetes?

A disorder where the pancreas fails to produce sufficient insulin

What is Type 2 diabetes?

Where body cells no longer respond to insulin produced by the pancreas

How do you treat Type 1 diabetes?

Through insulin injections

How do you treat Type 2 diabetes?

Through a carbohydrate-controlled diet and exercise regime

What is oestrogen?

The main female reproductive hormone produced in the ovary

What is ovulation?

Where a mature egg is released

What is testosterone?

The main male reproductive hormone produced by the testes and it stimulates sperm production

Name the hormones involved in the menstrual cycle

Follicle stimulating hormone (FSH), Luteinising hormone (LH), Oestrogen, Progesterone

What does Follicle stimulating hormone (FSH) cause?

The maturation of an egg in the ovaries

What does Luteinising hormone (LH) do

Stimulates the release of the egg

What is the role of Oestrogen and Progesterone?

They are involved in maintaining the uterus lining

What do oral contraceptives do?

Contain hormones to inhibit FSH production so that no eggs mature

How do injection, implant or skin patch contraceptives work?

By slowly releasing progesterone to inhibit the maturation and release of eggs for a number of months or years

Name two barrier methods of contraception

Condom, diaphragms

What is an intrauterine device?

A device that prevents the implantation of an embryo or releases a hormone

What do spermicidal agents do?

Kill or disable sperm

HT What are the four steps of In Vitro Fertilisation (IVF) treatment?

A mother is given FSH and LH to stimulate maturation of several eggs, eggs are collected from the mother and fertilised by sperm from the father in the laboratory, the fertilised eggs develop into embryos. One or two embryos are inserted into the mother's uterus

HT Give three negative about IVF

Emotionally and physically stressful, success rates are not high, can lead to multiple births which are a risk to both babies and the mother

HT What is adrenaline?

A hormone produced by the adrenal gland in times of fear or stress

HT What are the effects of adrenaline?

Increases heart rate, boosts the delivery of oxygen and glucose to the brain and muscles

HT What is thyroxine?

A hormone produced by the thyroid gland that stimulates basal metabolic rate

HT How are thyroxine levels controlled?

By negative feedback

What process leads to the formation of non-identical cells?

Meiosis

What process leads to the formation of identical cells?

Mitosis

What are the male gametes in animals?

Sperm cells

What are the female gametes in animals?

Egg cells

What are the male gametes in plants?

Pollen cells

What are the female gametes in plants?

Eggs cells

Which reproduction process involves the mixing of genetic material?

Sexual reproduction

Which reproduction process involves no mixing of genetic material?

Asexual reproduction

What is formed when cells in reproductive organs divide by meiosis?

Gametes

What happens to the number of chromosomes in gametes during meiosis?

It halves

What happens to gametes during fertilisation?

They join to restore the normal number of chromosomes

After fertilisation how does the new cell divide?

By mitosis

What is the basic structure of DNA?

A polymer made up of two strands forming a double helix

What is a gene?

A small section of DNA on a chromosome that controls a characteristic of that organism

What is a genome?

The entire genetic material of an organism

What is a chromosome?

A structure that contains the DNA of an organism

What is an allele?

The different form of a single gene

What is a phenotype?

The alleles present in an organism

What do we mean by a dominant allele?

A characteristic that is always expressed

What is a recessive allele?

A characteristic that is only expressed if two copies of the allele are present

What are homozygous alleles?

Where in an organism, two alleles are the same

What are heterozygous alleles?

Where in an organism, two alleles are different

What is polydactyly?

Having extra fingers or toes

Is polydactyly a dominant or recessive allele?

Dominant

What is cystic fibrosis?

A disorder of cell membranes

Is cystic fibrosis a dominant or recessive allele?

Recessive

How many pairs of chromosomes are there in the human body?

23

What sex is XX?

Female

What sex is XY?

Male

What is variation?

Differences in the characteristics of individuals in a population

What causes variation?

Differences in the genes inherited, the conditions in which they have developed or a combination of both

Describe the genetic variation within a population of a species

Usually extensive

How does variation occur?

Through mutations

How often do mutations occur?

Continuously

What is evolution?

A change in inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

What is the theory of evolution by natural selection?

That all species of living things have evolved from simple life forms that first developed more than three billion years ago

When does one species form into two new species?

When the one species becomes so different in phenotype that they can no longer interbreed to produce fertile offspring

What is selective breeding?

The process by which humans breed plants and animals for particular genetic characteristics

What is a danger of selective breeding?

'Inbreeding' where some breeds are particularly prone to disease or inherited defects

List four desired characteristics from selective breeding

Disease resistance in food crops, animals that produce more meat or milk, domestic dogs with a gentle nature, large or unusual flowers

What is genetic engineering?

A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desire characteristic

What are genetically modified crops?

Crops that have had their genes modified by genetic engineering

What are typical characteristics of genetically modified crops?

Resistance to insect attack, resistance to herbicides, increased yields

What is the evidence for evolution?

Fossils and antibiotic resistance in bacteria

What are fossils?

The 'remains' of organisms from millions of years ago, which are found in rocks

How are fossils formed?

From parts of organism that have not decayed, where parts of an organism are replaced by minerals as they decay or as preserved traces of organisms, such as footprints, burrows and rootlet traces

What is extinction?

When there are no remaining individuals of a species still alive

What factors contribute to the extinction of a species?

Environment changes, new predators, a new disease, they cannot compete with another species for food, a catastrophic event (like a volcanic eruption)

Why can bacteria evolve quickly?

Because they reproduce at a fast rate

What is MRSA?

A relatively common 'superbug' that is really hard to get rid of

Who developed the system of classification of living things?

Carl Linnaeus

Name the seven parts of the classification system

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

How are organisms names?

By the binomial system of genus and species

Who developed the 'three-domain system' of classification?

Carl Woese

Name the three domains developed by Carl Woese

Archaea, Bacteria and Eukaryota

What are Archaea?

Primitive bacteria usually living in extreme environments

What are four examples of Eukaryota?

Protists, fungi, plants and animals

Define ecosystem

The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment

What do plants in a community compete with each other for?

Light, space, water, mineral ions

What do animals in a community compete with each other for?

Food, mates, territory

What is interdependence?

Where in a community each species depends on other species such that if one species is removes it affects the whole community

What is a stable community?

One where all the species and environmental factors are in balance so that the population sizes remain fairly constant

List eight abiotic factors

Light intensity, temperature, moisture levels, soil pH, mineral content, wind intensity and direction, carbon dioxide levels (for plants), oxygen levels (for aquatic animals)

List four biotic factors

Availability of food, new predators arriving, new pathogens, one species outcompeting another so that numbers are no longer sufficient to breed

What are adaptations?

Features that organisms have that enable them to survive in the conditions in which they normally live

Name the three types of adaptation

Structural, behavioural, functional