AQA GCSE Biology (4401) Unit B1

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Name:

Inheritance and health

Genes which we inherit from

our parents also affect our

health eg cholesterol level.

Losing weight

People lose weight when:

energy in food eaten ˂ energy used by body.

Exercise increases the energy

used by the body, so helps us

lose weight.

Healthy diet A healthy diet contains the right balance of different foods. Carbohydrates, fats and proteins release energy and are used to build cells. Fruit and vegetables are a good source of vitamins and minerals.

B1 Diet and exercise

Poor diet

A person is malnourished if

their diet is not balanced.

This can mean a person is

overweight or underweight.

Unbalanced diets can lead to

deficiency diseases (eg scurvy

– lack of vitamin C) or heart

disease and type 2 diabetes etc.

Metabolic rate This is the rate at which chemical reactions occur inside our cells. Increasing exercise, increases metabolic rate. Muscle cells have a higher metabolic rate than fat cells. So people with a higher proportion of muscle to fat have a higher metabolic rate.

Infectious diseases Infectious diseases can be passed from one person to another eg coughs, sneezes, infected water/food. Pathogens are microorganisms that cause infectious diseases.

B1 Defence against infectious diseases: Part 1 Semmelweis – was a doctor in the 1850’s.

He recognised the importance of hand-

washing in preventing the spread of

infectious diseases in hospitals.

Today hand-washing in

hospitals helps to stop

the spread of antibiotic

resistant bacteria like MRSA.

Bacteria - are single celled microbes that reproduce rapidly inside our body. They make us ill by destroying our cells and making toxins (poisons).

Defence against pathogens

White blood cells defend us in 3 ways:

1. Making antitoxins (neutralise toxins).

2. Making antibodies (which bind to antigens on the surface of pathogens, destroying them).

3. Ingesting pathogens.

Viruses

Can only reproduce

inside our body cells.

They destroy the cells

which they invade making

us feel ill.

The immune system: White blood cells produce specific antibodies to kill each type of pathogen. (Each type of antibody can only bind to one specific type of antigen). Sketch a specific

antibody against the pathogen

Immunisation graph: describe and explain the shape of the curve

Immunisation People can be immunised against some diseases. A vaccine contains small amounts of dead or inactive pathogens. After being vaccinated our white blood cells make antibodies to destroy the pathogen. If you become re-infected with the pathogen white blood cells are stimulated to rapidly make a large quantity of antibody, making you immune to the disease. The MMR vaccine is used to protect children against 3 viruses; measles, mumps and rubella. If most of a population are vaccinated and become immune to a pathogen, its spread is greatly reduced.

Painkillers Paracetamol and other painkillers help to relieve the symptoms (eg headache, high temperature) of some infectious diseases. Painkillers do NOT kill pathogens. Antibiotics Antibiotics are drugs that kill infectious bacteria inside the body. Thus, antibiotics like penicillin help to cure bacterial diseases. Antibiotics have NO EFFECT on VIRUSES because viruses live inside body cells and are inaccessible to antibiotics. It is hard to develop drugs that kill viruses without also damaging body cells.

After 1st injection antibody levels slowly rise, peaking after 3 weeks. It takes time for the white blood cells to make the specific antibody needed against the pathogen.

After 2nd injection a larger amount of antibody is made more rapidly. White blood (memory) cells quickly make antibody making you immune.

B1 Defence against infectious diseases: Part 2

Antibiotic resistance

Some strains of bacteria are no longer killed by antibiotics. They have developed resistance to antibiotics through natural selection.

Sort the sequence:

1 Resistant bacteria reproduce

2. Antibiotic used.

3. Mutation causes a new

resistant strain of bacteria

to appear.

4. Resistant bacteria population

increases.

5. Non-resistant bacteria die,

resistant bacteria survive.

Mutations (HT only)

Mutations (random changes in DNA) produce new strains of pathogens. Antibiotics (against bacteria) and vaccines (against bacteria or viruses) may no longer be effective. As people are no longer immune, new strains can spread rapidly.

Using antibiotics effectively Doctors must: Use specific antibiotics against specific bacteria (choose the most effective antibiotic). Avoid overuse of antibiotics. Avoid non-essential use (eg. non-serious throat infections) Together this will help to slow down the rate of development of resistant bacteria strains. Hopefully in the future new antibiotics can be developed to kill resistant strains of bacteria.

Growing microbes – uncontaminated cultures of microbes are needed to test antibiotics + disinfectants To avoid contamination: 1. Sterilise petri dishes and culture media to kill unwanted microbes. 2. Sterilise the inoculating loop by heating in a flame, before using it to transfer bacteria to the petri dish. 3. Seal the dish with tape to stop pathogens entering from the air. Incubate microbes at 25 °C to reduce the chance of growing harmful pathogens (in industry 40 °C allows faster microbe growth).

3 2 5 1 4

B1 Antibiotic resistance and growing bacteria

Spinal cord

Receptors

Special cells called receptors detect changes in the environment called stimuli.

B1: Nervous system Part 1 Label the receptor cell

Which stimulus does this receptor detect? light

Neurones

Neurones are nerve cells. They pass electrical signals rapidly from receptors to the CNS and from the CNS to effectors.

Synapse (gap between two neurones). Describe how an impulse travels across a synpase. Label the direction of the impulse.

Organ with receptors

Stimulus detected by receptors

Eyes Light

Ears Sound

Ears Balance + position

Tongue + nose

Chemicals for taste + smell

Skin Touch, pain, pressure+

temperature

CNS: Label the two parts of the central nervous system (CNS).

Chemical transmitter is released and diffuses across the synapse.

membrane

nucleus

cytoplasm

brain

Remember

Effectors are usually muscles

(which contract) or glands (that secrete

chemicals eg hormones or enzymes).

They bring about the response.

B1: Nervous system Part 2

Reflexes

Reflexes are rapid automatic (not involving the brain) responses.

A person is hit below the knee (P). On the reflex arc diagram identify A, B, C, + label the relay neurone and effector.

Response

Complete the pathway for a typical reflex action and when you touch a hot object.

Stimulus

CNS

Effector

Receptor

Hot object

Pain/temp’

CNS

arm muscle

Move away

Sensory neurone Sensory neurone

Motor neurone Motor neurone

C= Spinal cord

Relay neurone

A = sensory neurone

B= Motor neurone

effector

Our body must control its internal conditions carefully. This is called homeostasis.

B1 Control in the human body

Internal condition to

control

Details

Water Lost via lungs (breathing out), skin (in sweat) and kidneys (in urine)

Ions Ions are lost in sweat. Excess ions from our diet are lost via kidneys in urine.

Temperature Must be kept constant (37 °C) so that enzymes work best.

Blood sugar Must be kept constant to provide cells with energy source (for respiration).

“I said ions, not irons!”

B1 Female sex hormones

Hormones Hormones are: 1. Chemical messengers 2. Secreted by glands 3. Transported in the blood 4. Specific and only act on target organs.

The pituitary gland This gland is found in the brain. It secretes FSH and LH. Both hormones travel in the blood to their target organ the ovary.

The menstrual cycle

The monthly changes in the lining of the uterus and the development and release of an egg are regulated by several hormones.

Hormone Released by

Effects

Follicle stimulating hormone (FSH)

Pituitary gland

Stimulates an egg to mature in the ovary.

Stimulates oestrogen production.

Oestrogen Ovary Stimulates LH release.

(Can inhibit FSH, so used in the pill)

Luteinising hormone (LH)

Pituitary gland

Peak triggers ovulation.

Oral contraceptives

Oral contraceptives are pills taken to prevent pregnancy. They may contain the hormones oestrogen and progesterone. These inhibit FSH production so

that no eggs

mature in

the ovaries.

B1 Using hormones

Fertility drugs Some women are unable to get pregnant because their FSH levels are too low. This stops their eggs from maturing. These women may be given the hormones FSH and LH as a “fertility drug”. This allows her eggs to mature. Fertility treatment is often used as part of IVF.

“Pill” problems The first type of birth control pills developed had high levels of oestrogen. This resulted in women suffering side effects. Modern pills contain a low dose of oestrogen or contain only progesterone. These have fewer side effects.

Fertility treatment issues Contraceptives help to control human population, reducing poverty. But, some women suffer side effects. Some religions object to contraception as it denies life. Multiple births from IVF can result in premature, unhealthy babies. Ethical issues arise, such as what to do with spare embryos.

IVF (in vitro fertilisation)

Sort the sequence FSH + LH given to woman

Several eggs are stimulated to mature

Eggs are collected from ovaries

Father’s sperm is collected

Sperm is used to fertilise eggs in a dish.

Fertilised eggs develop into embryos

One or two embryos are inserted into mothers uterus

5 3 7 1 2 6 4

Plant hormones

Plants are sensitive to light, moisture and gravity. Responses of plants to these stimuli are due to the unequal distribution of the hormone auxin.

B1 Control in Plants

Moisture

Plant roots grow towards moisture. (hydrotropism).

Light

Shoots grow towards light. This response is called phototropism.

1. Auxin is made in the shoot tip.

2. Light makes auxin build up on the shady side of the shoot.

3. Cells on the shady side grow faster.

4. Shoot bends towards light.

Gravity

Shoots grow against gravity.

Roots grow towards gravity. These responses are called gravitropism (or geotropism).

1. Auxin is made in root tip.

2. Gravity makes auxin build

up on the lower side of the

root.

3. Cells on the lower side

grow slower (auxin inhibits).

4. Root bends down towards the force of gravity.

Uses of plant hormones

Synthetic auxins are used as selective weed killers. They kill broad leaved plants (like dandelions), but not narrow leaved ones (like grass) .

Auxins are used as rooting hormones.

Dipping cuttings in hormone rooting

powder stimulates root growth.

New drugs

Scientists are continually developing new drugs. Each new medical drug must be tested before use. Tissues and animals are often used as models to predict how drugs may affect humans.

B1 Drugs Part 1

Double blind trials

Some patients are given a placebo, which does not contain the drug. Neither the doctor or the patients know who has been given the drug or placebo.

Thalidomide This drug was originally developed as a sleeping pill. Without being tested, it was used to prevent morning sickness in pregnant women. Unfortunately, many babies were born with severe limb abnormalities. Thalidomide is now banned for use by pregnant women. Recently thalidomide has been used to treat the bacterial disease, leprosy.

Many patients (clinical trial)

Complete the steps involved in testing a new drug.

Cells + tissues

Healthy humans

A few patients

Animals

Is drug toxic or effective?

Find side effects + dose

Is drug safe at low dose?

Does drug treat disease?

Optimum dose

What drug is tested on Aim of test

Drugs

A drug is a chemical that alters the way your body works.

Some drugs are addictive. Addiction is when you become physically or mentally dependent on a drug.

Addicts suffer from withdrawal symptoms if they stop using drugs.

B1 Drugs Part 2

Cannabis

Cannabis is an illegal drug.

Smoking cannabis may cause mental health problems. There is evidence that using drugs like cannabis can lead to use of hard drugs such as cocaine and heroin which are highly addictive.

Alcohol

Is a legal drug. Like cannabis,

alcohol slows down nerve impulses,

increasing your reaction time.

Alcohol addiction can lead to liver disease.

Statins

These are drugs which can be taken to lower blood cholesterol levels. This helps to lower the

risk of heart and circulatory diseases.

Drug use by athletes

Anabolic steroids are illegally used by some athletes to increase their muscle growth. Stimulants are also banned for use in many sports because they increase heart rates and boost performances.

Nicotine Is a legal drug found in cigarettes. Like caffeine and cocaine, nicotine can speed up nerve impulses and act as a stimulant. Addiction to nicotine means that many smokers find it hard to give up and many suffer from lung cancer.

Other recreational drugs

Misuse of ecstasy, cannabis and heroin can have adverse effect s on the heart and circulatory system

Competition

Plants compete with each other for light, space, water and mineral ions (from the soil).

Animals compete with each other for food, mates and territory.

B1 Adaptations Part 1

Adaptations in animals to survive dry environments eg desert fox Large ears increase the surface area, increasing heat lost by radiation. Thin coat and body fat reduce insulation and help heat loss by radiation. Camouflage allows this predator to hide from its prey.

Adaptations by plants to survive dry environments 1. Leaves reduced to spines. The small surface area reduces water loss by evaporation. 2. Water storage tissues. 3. Extensive roots absorb water from the soil.

Adaptations in animals to survive arctic environments eg polar bear.

Small ears help to reduce the surface area, reducing heat lost by radiation.

Thick coat and body fat layers insulate, reducing heat lost by radiation.

Camouflage allows

this predator to hide

from its prey.

B1 Adaptations Part 2

Extremophiles

Some organisms live in extreme environments. These extremophiles may be tolerant to high levels of salt, high temperatures or high pressures.

Many extremophiles are microbes. For example bacteria living near deep sea vents have enzymes that do not denature at high temperatures, even up to 80 °C.

Adaptations to deter herbivores/predators

Some plants have sharp thorns to deter herbivores.

Adaptations to deter predators

The coral snake is poisonous. Its colours act as warning and deters its predators. This is exploited by the milk snake which mimics the coral snake. It lives in the same habitat, has similar markings but is not poisonous.

Changes in the environment affect the distribution of organisms.

Global warming has affected the migration and distribution of some birds.

Loss of habitats and use of pesticides has led to a decline in pollinating insects such as bees.

B1 Environmental change

Non-living indicators of environmental change.

Scientists can used equipment to measure some changes in the environment.

An oxygen probe detects changes

in oxygen.

A max-min thermometer is used

to record the range of daily

temperatures.

A rainfall gauge helps to

record rainfall.

Living pollution indicators

Some living organisms act as pollution indicators. For example lichen growth and biodiversity is reduced by the presence of sulphur dioxide/acid rain.

Some invertebrates are water pollution indicators, as they need high levels of dissolved oxygen to survive. Polluted water contains less oxygen, so tends to contain fewer invertebrates such as shrimps and mayfly larvae.

The Sun The Sun’s radiation is the source of energy for most food chains. Plants and algae absorb light energy and transfer it to chemical energy during photosynthesis. This energy is stored in the plants biomass eg starch, sugars and cellulose. The transfer of energy from the Sun to the plant is very inefficient. Most light is the wrong wavelength for plants to absorb and only about 5 % of the Sun’s energy is converted to chemical energy in the plants biomass.

B1 Energy in biomass

Biomass = mass of living material at each stage in a food chain.

Pyramids of biomass: show the amount of biomass at each stage in a food chain.

Draw a pyramid of biomass for the food chain: Rose→ aphid →robin →cat

Loss of energy and biomass

At each stage in a food chain energy and biomass are lost.

Some biomass is lost as waste (eg. faeces) or in parts not eaten.

Some energy lost during respiration to provide energy for movement etc . Most of this “lost” energy is transferred to the surroundings as heat.

Rose

aphid

Robin

Cat

Detritus feeders + microbes digest waste and dead organisms, releasing

useful nutrients for plants

Decay

Decay occurs when organic materials are broken down (digested) by microorganisms (bacteria and fungi).

Microorganisms are more active when conditions are warm, moist and aerobic (oxygen is present).

Decay releases and recycles materials needed for plants to grow including nitrates and the gas carbon dioxide.

B1 Decay and the carbon cycle

Carbon cycle

photosynthesis

death

respiration

combustion

Carbon in plant biomass as fats, sugars + proteins

Carbon dioxide

Carbon in animal as fats, sugars +

proteins

Inheritance

Offspring have similar characteristics to their parents due to the genes which they inherit. During sexual reproduction, genes are passed on via the parents sex cells (gametes).

B1 Why organisms are different

Variation

Differences between individuals of the same species are due to the genes they have inherited, the environment or a combination of both.

Types of reproduction

Inside the nucleus

The nucleus of each cell

contains the genetic

material (DNA) arranged

as threads called chromosomes.

Each chromosome carries many genes which control characteristics (eg. eye colour). Label the genes.

Characteristic Reason for variation

(genes, environment or both)

Plant height G + E

Eye colour G

Accent E

Body mass G + E

Feature Type of reproduction

Sexual Asexual

Parent number 2 1

Genetic variation in offspring

yes None (clones)

Sex cells yes no

Clones

Clones are genetically identical organisms. All organisms produced by asexual reproduction are clones of their parent.

B1 Cloning Part 1

Tissue culture

Small groups of cells from

part of a plant can be

grown on nutrient medium

with plant hormones.

Whole plants

develop.

Cuttings

Gardeners can produce large numbers of plants quickly and cheaply by taking cuttings. New plants are clones, genetically identical to the parent plant.

Embryo transplants

Early stage embryo

is split

Identical embryos develop and are

transplanted into the uterus of host mothers

Identical clones are born from each host

mother

Remove nucleus from egg cell

“Empty” egg Insert skin cell nucleus into empty egg cell.

Electric shock stimulates cell division and an embryo forms

Insert embryo into uterus

Foal is a clone of “A”

Animal “A” Adult cell cloning This was like the method used to make “Dolly” the sheep. The nucleus is removed from an adult body cell of the animal to be cloned. For Dolly the sheep the body cell was an udder cell. In this example a skin cell is used.

B1 Cloning part 2

B1 Genetic engineering

Genetic engineering to make herbicide resistant plants

Genetically modified (GM) crop issues GM crops have been made which are resistant to herbicide (weed killer). Spraying the crop with herbicide kills the weeds, reducing competition for light, minerals etc. So crop yields increase. Some GM crops have genes that make them resistant to insect attack. This also increases crop yields. BUT… some people are concerned about the effects of GM food on health. GM crop plants may pass on the inserted gene to wild plants. Using GM resistant crops may encourage the use of herbicides.

Genetic engineering

Genes are “cut out” from chromosomes of one organism and transferred to the nucleus of another organism (eg animal, plant or microbe).

The spider gene is inserted into an egg or embryo (from a goat).

The embryo develops into a GM goat which contains the spider gene in its cells.

Making a GM goat containing a spiders gene!

Enzymes are used to cut out a spider gene from its chromosome.

Apart from having the herbicide-resistance gene, the herbicide-resistant plants are identical to the herbicide-susceptible plants. All their cells have the same DNA as the single parent plant as no sex cells were used.

Evolution: The theory of evolution states that all species alive today have evolved from the first simple life forms on Earth over a long period of time.

B1 Evolution part 1

Lamarck’s theory

Lamarck believed that

species evolved

because changes that

occurred in an organism during

its lifetime could be inherited.

Darwin’s theory: Darwin’s theory states that evolution occurs by natural selection. Variation exists within all populations. Those individuals which are better adapted, survive and reproduce, increasing in number.

Variation exists in the rat population (due to mutations).

Some rats are resistant to poison.

Resistant rats survive and breed.

Offspring inherit poison resistance gene (allele).

Numbers of rats resistant to poison increase.

Stretching for food led

to more neck use

More use led to neck getting

longer

Longer neck characteristic was passed to offspring

Darwin’s struggle

Darwin was the first scientist to state that humans and other primates had common ancestors.

Darwin’s theory of evolution was only gradually accepted because…

1. It challenged the idea

that God made all the

the animals and plants

that live on Earth.

2. there was

insufficient evidence.

3. the mechanism of

inheritance and

variation was not

known until 50 years

later.

B1 Evolution part 2 + classification

Lamarck and Darwin made different theories of evolution. Scientists may produce different hypotheses to explain similar observations. It is only when these hypotheses are investigated that data will refute or support hypotheses.

Classification

Studying the similarities and differences between

organisms allows us to classify living organisms

into animals, plants and microorganisms, and helps

us to understand evolutionary and ecological

relationships. Models such as evolutionary trees allow us to suggest relationships between organisms.

Which is the closest relative to fur seals? Sea lions

Mutations

Where new forms of a gene result from mutation there may be relatively rapid change in a species if the environment changes. eg. Air pollution made tree bark sooty during the Industrial

revolution. Mutant black moths

evolved and increased in numbers.