Paper 2

What is Homeostasis? -

What is homeostasis?

The regulation of internal conditions to maintain a stable interval environment in resposne to internal + external changes.

What is Homeostasis? -

What conditions in the body are controlled by homeostasis?

Blood glucose concentration, Body temperature, Water levels, Ion content.

What is Homeostasis? -

Why is homeostasis important?

To maintain optimal conditions for enzyme action + cell function.

The Nervous System -

What is the function of the nervous system?

To detect stimuli, process information, + coordinate a response using electrical impulses.

The Nervous System -

What are the three main types of neurones + their functions?

Sensory neurone: Carries impulses from receptor to CNS

Relay neurone: Connects sensory to motor neurones in the CNS

Motor neurone: Carries impulse from CNS to effector

The Nervous System -

What are receptors + effectors?

Receptors: Cells that detect stimuli

Effectors: Muscles / glands that carry out responses

The Nervous System -

What is a reflex arc + why is it important?

An automatic + rapid response to a stimulus that bypasses the brain to protect the body from harm.

The Nervous System -

Sequence the path of a reflex action.

Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.

The Nervous System -

What is a synapse + how do impulses cross it?

A gap between neurones where chemicals (neurotransmitters) are released to transmit the signal.

Nervous System Practical (Reaction Time) -

What is measured in the reaction time practical?

The time taken to respond to a stimulus, e.g. catching a ruler.

Nervous System Practical (Reaction Time) -

What variables should be controlled in this experiment?

Same ruler, same height, no distractions, same hand, rest before trial.

Nervous System Practical (Reaction Time) -

How can caffeine affect reaction time?

It can reduce reaction time (faster response), but this should be tested w/ care + under controlled conditions.

The Endocrine System -

What is the endocrine system?

A system of glands that secrete hormones into the blood to regulate body processes.

The Endocrine System -

What is hormone?

A chemical messenger secreted by glands + transported in the blood to target organs.

The Endocrine System -

Name 5 major endocrine glands + one hormone they produce.

Pituitary gland - many hormones, including FSH/LH

Pancreas - insulin + glucagon

Adrenal gland - adrenaline

Thyroid - thyroxine

Ovaries/testes - oestrogen/testosterone

Controlling Blood Glucose -

What does insulin do?

Lowers blood glucose by promoting glucose uptake + storage as glycogen in the liver.

Controlling Blood Glucose -

What does glucagon do?

Raises blood glucose by breaking down glycogen into glucose in the liver.

Controlling Blood Glucose -

What is Type 1 diabetes + how is it treated?

A disorder where the pancreas produces little / no insulin; treated w/ insulin injections.

Controlling Blood Glucose -

What is Type 2 diabetes + how is it treated?

A condition where body cells no longer respond to insulin; treated w/ diet, exercise, + sometimes medication.

Thermoregulation & Water Balance -

How does the body cool down when it’s too hot?

Sweat is produced + evaporates. Blood vessels dilate (vasodilation) to release heat.

Thermoregulation & Water Balance -

How does the body respond to being too cold?

Hairs strand up to trap air, Blood vessels constrict (vasoconstriction), Shivering generates heat from respiration.

Hormones in Human Reproduction -

What are the four key hormones in the menstrual cycle?

FSH: Stimulates egg maturation + oestrogen production

Oestrogen: Repairs uterus lining; inhibits FSH; stimulates LH

LH: Triggers ovulation

Progesterone: Maintains uterus lining + inhibits LH/FSH

Hormones in Human Reproduction -

What is ovulation + when does it occur?

The releases of an egg from the ovary, usually around day 14 of the cycle.

Contraception -

Name 3 hormonal methods of contraception.

Combined pill, Contraceptive patch, Injection / implant.

Contraception -

How do hormonal contraceptives work?

They prevent ovulation + make the uterus lining less suitable for implantation.

Contraception -

Name 3 non-hormonal methods of contraception.

Barrier methods (condoms, diaphragm)

Intrauterine device (IUD)

Surgical methods (sterilisation)

Contraception -

What are the advantages + disadvantages of hormonal contraception?

Very effective, long-term options available

May have side effects (e.g. mood changes, weight gain)

Fertility Treatments -

How can hormones be used to treat infertility?

FSH + LH can be given to stimulate egg production + ovulation.

Fertility Treatments -

What is IVF + how does it work?

In vitro fertilisation involves collecting eggs, fertilising them outside the body, + implanting embryos into the uterus.

Fertility Treatments -

What are the pros + cons of IVF?

Can help couples have children.

Expensive, low success rate, emotional stress, multiple births.

Negative Feedback -

What is negative feedback?

A control mechanism where a change is detected + responses restore conditions back to normal.

Negative Feedback -

Give two examples of negative feedback in the body.

Thryoxine regulation (controls metabolism).

Blood glucose control using insulin + glucagon.

DNA & the Genome -

What is DNA?

A polymer made of two strands forming a double helix, carrying genetic instructions.

DNA & the Genome -

What is a gene?

A small section of DNA that codes for a specific protein.

DNA & the Genome -

What is the genome?

The entire set of genetic material in an organism.

DNA & the Genome -

Why is understanding the human genome important?

Helps in identifying genes linked to diseases, understanding human evolution, developing personalised medicine.

Reproduction -

What are the two types of reproduction?

Asexual: One parent, no genetic variation

Sexual: Two parents, produces variation

Reproduction -

What happens in sexual reproduction?

Gametes (sperm + egg) fuse during fertilisation, combining genetic material.

Reproduction -

What is meiosis?

A type of cell division that produces four genetically different haploid gametes.

Reproduction -

Where does meiosis occur?

In the ovaries + testes to produce egg + sperm cells.

Reproduction -

How does meiosis differ from mitosis?

Meiosis produces gametes w/ half the chromosome number; mitosis produces identical cells for growth/repair.

Inheritance -

What is an allele?

Different versions of the same gene.

Inheritance -

What do dominant + recessive mean?

Dominant: Always expressed if present

Recessive: Only expresssed if two copies are present

Inheritance -

What is a genotype + a phenotype?

Genotype: The genetic makeup

Phenotype: The physical expression

Inheritance -

What does homozygous + heterozygous mean?

Homozygous: Both alleles are the same

Heterozygous: Two different alleles

Inheritance -

What is a Punnett square used for?

To predict the probability of inherited traits in offspring.

Inherited Disorders & Sex Determination -

Give two examples of inherited disorders.

Cystic fibrosis - caused by a recessive allele

Polydactyly - caused by a dominant allele

Inherited Disorders & Sex Determination -

What is embryo screening?

Testing embryos for genetic disorders before implantation / birth.

Inherited Disorders & Sex Determination -

What are some issues w/ embyro screening?

Ethical concerns (designer babies)

Expensive

May lead to discrimination

Inherited Disorders & Sex Determination -

How is sex determined in humans?

XX = female

XY = male

(Male gamete determines sex)

Variation & Evolution -

What causes variation in a species?

Genetic factors (inherited genes)

Environmental factors (e.g. diet)

A combination of both

Variation & Evolution -

What is evolution?

The gradual change in the characteristics of a population over time.

Variation & Evolution -

Who proposed the theory of evolution by natural selection?

Charles Darwin.

Variation & Evolution -

What is natural selection?

Organisms w/ advantages traits survive + reproduce, passing on those traits.

Variation & Evolution -

What is speciation?

The formation of a new species when populations become so different they can’t interbreed.

Selective Breeding & Genetic Engineering -

What is selective breeding?

Humans choosing organisms w/ desired traits to breed, to produce offspring w/ those traits.

Selective Breeding & Genetic Engineering -

Give two disadvantages of selective breeding.

Reduces genetic diversity

Increased risk of inherited diseases

Selective Breeding & Genetic Engineering -

What is genetic engineering?

Modifying the genome of an organism by inserting a gene from another organism.

Selective Breeding & Genetic Engineering -

Give one example of a genetically engineered organism.

Insulin-producing bacteria

GM crops w/ disease resistance / higher yields

Selective Breeding & Genetic Engineering -

What are some concerns about genetic engineering?

Unpredictable long-term effects

Ethical concerns

Potential impact on biodiversity

Fossils & Extinction -

How are fossils formed?

From hard parts not decayed

Impressions in rock

Replacement by minerals

In conditions preventing decay

Fossils & Extinction -

What can fossils tell us?

About how organisms have changed + evolved over time.

Fossils & Extinction -

Why is the fossil record incomplete?

Many organisms were soft-bodied

Conditions weren’t right for fossilation

Fossils may have been destroyed

Fossils & Extinction -

What can cause extinction?

New predators

New diseases

Environmental changes

Human activity

Ecosystems & Interdependence -

What is an ecosystem?

A community of organisms interacting w/ the biotic + abiotic elements of their environment.

Ecosystems & Interdependence -

Define “community” in ecological terms.

All the populations of different species living + interacting in a habitat.

Ecosystems & Interdependence -

What is interdependence?

The way in which species rely on each other for food, shelter, pollination, etc.

Ecosystems & Interdependence -

What is a stable community?

One where the population sizes remain relatively constant due to balanced biotic + abiotic factors.

Abiotic & Biotic Factors -

What are abiotic factors? Give 3 examples.

Non-living factors:

Light intensity

Temperature

Water availability

Abiotic & Biotic Factors -

What are biotic factors? Give 3 examples.

Living factors:

New predators

Competition

New pathogens

Abiotic & Biotic Factors -

How can a change in abiotic factors affect a community?

Can reduce population sizes by affecting growth or reproduction.

Abiotic & Biotic Factors -

How can biotic factors cause changes in population size?

Changes in predation, disease / competition can increase / decrease populations.

Adaptations -

What is an adaptation?

A feature that helps an organism survive + reproduce in its environment.

Adaptations -

What are the three types of adaptations?

Structural (e.g. thick fur)

Behavioural (e.g. migration)

Functional (e.g. concentrated urine)

Adaptations -

What is an extremophile?

An organism that can live in extreme environments, such as high temperature, salinity, / pressure.

Organisation of an Ecosystem -

What is a producer?

An organism (usually a green plant / algae) that produces its own food via photosynthesis.

Organisation of an Ecosystem -

What is a primary consumer?

An organism that eats producers - usually a herbivore.

Organisation of an Ecosystem -

What is a trophic level?

The position of an organism in a food chain.

Organisation of an Ecosystem -

What is the role of decomposers?

Break down dead organisms + waste materials to recycle nutrients.

Organisation of an Ecosystem -

How do decomposers break down materials?

They secret enzymes to digest materials externally + absorb the nutrients.

Pyramids of Biomass & Energy Transfer -

What does a pyramid of biomass show?

The relative mass of living material at each trophic level.

Pyramids of Biomass & Energy Transfer -

Why is energy transfer between trophic levels inefficient?

Only about 10% of energy is transferred; most is lost via respiration, movement, / as heat.

Pyramids of Biomass & Energy Transfer -

How can biomass be lost in a food chain?

Through:

Not all material being eaten

Waste

Movement + respiration

The Carbon Cycle -

What are the main processes in the carbon cycle?

Photosynthesis (removes CO2)

Respiration (releases CO2)

Combustion (releases CO2)

Decomposition (releases CO2)

The Carbon Cycle -

Why is the carbon cycle important?

It recycles carbon, a vital element in all living organisms.

The Water Cycle -

Name the key stages of the water cycle.

Evaporation

Condensation

Precipitation

Transpiration

The Water Cycle -

What is transpiration?

Loss of water vapour from plants via stomata.

Decay & the Cycle of Materials -

What factors affect the rate of decay?

Temperature

Oxygen availability

Moisture levels

Number of microorganisms

Decay & the Cycle of Materials -

What is compost?

Decayed organic matter used as a natural fertiliser.

Decay & the Cycle of Materials -

What is biogas + how is it produced?

A fuel produced by anaeorbic decay of biological material.

Environmental Change & Biodiversity -

What is biodiversity?

The variety of different species of organisms on Earth / w/in an ecosystem.

Environmental Change & Biodiversity -

Why is biodiversity important?

It ensures the stability of ecosystems by reducing dependence on one species.

Environmental Change & Biodiversity -

How do human activities reduce biodiversity?

Deforestation

Pollution

Overexploitation

Climate change

Environmental Change & Biodiversity -

What measures are being taken to protect biodiversity?

Breeding programmes

Habitat protection

Reduction of deforestation + waste

Recycling programmes

Pollution -

What are the main types of pollution?

Water pollution

Air pollution

Land pollution

Pollution -

How does pollution affect ecosystems?

It kills plants + animals, disrupts food chains, + reduces biodiversity.

Global Environmental Issues -

What causes global warming?

Increased greenhouse gases (CO2 + methane) trap heat in the atmosphere.

Global Environmental Issues -

What are the effects of global warming?

Rising sea levels

Habitat loss

Changes in migration patterns

Reduced biodiversity

Global Environmental Issues -

What is deforestation + why is it done?

Removal of forests for:

Farming

Timber

Biofuel production

Global Environmental Issues -

What are the environmental consequences of deforestation?

Less CO2 absorbed

More CO2 released

Reduced biodiversity