B1 RevisionLearning Intentions:• Basically all of B1.

B1.4 Interdependence and adaptation

B1.4.1 Adaptationsa) To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there.b) Plants often compete with each there for light and space, and for water and nutrients from the soil.c) Animals often compete with each other for food, mates and territory.

B1.4.1 Adaptationsd) Organisms, including microorganisms have features (adaptations) that enable them to survive in the conditions in which they normally live.e) Some organisms live in environments that are very extreme. Extremophiles may be tolerant to high levels of salt, high temperatures or high pressures.

B1.4.1 Adaptationsf) Animals and plants may be adapted for survival in the conditions where they normally live, eg deserts, the Arctic.Animals may be adapted for survival in dry and arctic environments by means of:■ changes to surface area■ thickness of insulating coat■ amount of body fat■ camouflage.Plants may be adapted to survive in dry environments by means of:■ changes to surface area, particularly of the leaves■ water-storage tissues■ extensive root systems.g) Animals and plants may be adapted to cope with specific features of their environment, eg thorns, poisons and warning colours to deter predators.

Each zone of this oak tree is home to a distinctive community of organisms.

The Polar Bear• Polar bears are well adapted for survival

in the Arctic. Their adaptations include:– A white appearance as camouflage from

prey on the snow and ice– Thick layers of fat and fur for insulation

against the cold– A small surface area to volume ratio, to

minimise heat loss– A greasy coat that sheds water after

swimming– Large furry feet to distribute their load and

increase grip on the ice.

The Camel• Camels live in deserts that are hot and dry during

the day, but cold at night. Their adaptations include:– Large, flat feet to spread their weight on the sand– Thick fur on the top of the body for shade, and thin

fur elsewhere to allow easy heat loss– A large surface-area-to-volume ratioto maximise

heat loss– The ability to go for a long time without water -

they don't store water in their humps, but they lose very little water through urination and perspiration

– The ability to tolerate body temperatures up to 42ºC

– Slit-like nostrils and two rows of eyelashes to help keep out sand.

The Cacti• Cacti are well adapted for survival in

the desert. Their adaptations include:– Stems that can store water–Widespread root systems that can

collect water from a large area.– In addition, cacti have spines instead of

leaves. These minimise the surface area and so reduce water loss by transpiration. The spines also protect the cacti from animals that might eat them.

The Venus Fly Trap• Venus fly traps are adapted to areas

poor in nitrates and phosphates. Their adaptations are:– A closing trap when insects fly into it,

caused by contact with trigger hairs.– Being able to digest insects.

B1.4.2 Environmental change

a) Changes in the environment affect the distribution of living organisms.b) Animals and plants are subjected to environmental changes. Such changes may be caused by living or non-living factors such as a change in a competitor, or in the average temperature or rainfall.

B1.4.2 Environmental change

c) Living organisms can be used as indicators of pollution:■ lichens can be used as air pollution indicators, particularly of the concentration of sulphur dioxide in the atmosphere■ invertebrate animals can be used as water pollution indicators and are used as indicators of the concentration of dissolved oxygen in water. d) Environmental changes can be measured using non-living indicators such as oxygen levels, temperature and rainfall.

How prey and predators are linked

• More prey • More food for predators • More predators survive and reproduce • More predators • More competition for food • Some predators die (starvation) • Fewer predators • More prey survive

Lichen

Crusty lichens can survive in more polluted air

Leafy lichens can survive a small amount of air pollution

Green, bushy lichens need really clean air

Blackspot Fungus

• Another indicator of air quality is the blackspot fungus on roses. Blackspot fungus grows well on roses in unpolluted areas.

• It is killed by the presence of sulphur dioxide that would be found in polluted air.

Indicators of water pollution• Scientists can take samples of the

invertebrate animals living in a river to see if it is polluted.

• Some invertebrates are able to live in polluted water and some are not.

Indicators of water pollutionPolluted water – cloudy, smelly with low levels of oxygen

Invertebrates found: Not many different species. Mostly worms and leeches.

Indicators of water pollutionSlightly polluted water – less cloudy and smelly, oxygen levels rising.

Invertebrates found: more species: molluscs (snails), some beetles.

Indicators of water pollutionClean water – clear water, high levels of oxygen.

Invertebrates found: Many different species. Will begin to find shrimps and mayfly larva which will not tolerate any pollution.

B1.5 Energy and biomass in food chains

B1.5.1 Energy in biomassa) Radiation from the Sun is the source of energy for most communities of living organisms. Green plants and algae absorb a small amount of the light that reaches them. The transfer from light energy to chemical energy occurs during photosynthesis. This energy is stored in the substances that make up the cells of the plants.b) The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass.

B1.5.1 Energy in biomassc) The amounts of material and energy contained in the biomass of organisms is reduced at each successive stage in a food chain because:■ some materials and energy are always lost in the organisms’ waste materials■ respiration supplies all the energy needs for living processes, including movement. Much of this energy is eventually transferred to the surroundings.

Food Chains• Food chains show the flow of

material in biomass and energy flow.• All life needs energy to stay alive.

Food Chains• Energy from the sun is absorbed by

green plants.• These are called producers.• Who are eaten by primary

consumers.• Who in turn are eaten by secondary

consumers.

REMEMBER• Energy cannot be created or

destroyed, it is only transferred.• Either up the food chain or out by

movement, excretion, etc.

• Describe how energy lost as it travels through a food chain.• Construct food webs.• Describe how farmers try to reduce energy loss.

B1.6 Waste materials from plants and animals

B1.6.1 Decay processesa) Living things remove materials from the environment for growth and other processes. These materials are returned to the environment either in waste materials or when living things die and decay.b) Materials decay because they are broken down (digested) by microorganisms. Microorganisms are more active and digest materials faster in warm, moist, aerobic conditions.c) The decay process releases substances that plants need to grow.d) In a stable community, the processes that remove materials are balanced by processes that return materials. The materials are constantly cycled.

Decay• Living things remove materials from

the environment for growth and other processes.

• These materials are returned to the environment either in waste materials or when living things die and decay.

Decay• Materials decay because they are

broken down (digested) by microorganisms.

• Microorganisms are more active and digest materials faster in warm, moist, aerobic conditions.

Decay• The decay process releases

substances that plants need to grow.• In a stable community, the processes

that remove materials are balanced by processes that return materials.

• The materials are constantly cycled.

B1.6.2 The carbon cyclea) The constant cycling of carbon is called the carbon cycle. In the carbon cycle:■ carbon dioxide is removed from the environment by green plants and algae for photosynthesis■ the carbon from the carbon dioxide is used to make carbohydrates, fats and proteins, which make up the body of plants and algae■ when green plants and algae respire, some of this carbon becomes carbon dioxide and is released into the atmosphere■ when green plants and algae are eaten by animals and these animals are eaten by other animals, some of the carbon becomes part of the fats and proteins that make up their bodies

B1.6.2 The carbon cycle■ when animals respire some of this carbon becomes carbon dioxide and is released into the atmosphere■ when plants, algae and animals die, some animals and microorganisms feed on their bodies■ carbon is released into the atmosphere as carbon dioxide when these organisms respire■ by the time the microorganisms and detritus feeders have broken down the waste products and dead bodies of organisms in ecosystems and cycled the materials as plant nutrients, all the energy originally absorbed by green plants and algae has been transferred■ combustion of wood and fossil fuels releases carbon dioxide into the atmosphere.

B1.7 Genetic variation and its control

B1.7.1 Why organisms are different

a) The information that results in plants and animals having similar characteristics to their parents is carried by genes, which are passed on in the sex cells (gametes) from which the offspring develop.b) The nucleus of a cell contains chromosomes. Chromosomes carry genes that control the characteristics of the body.

B1.7.1 Why organisms are different

c) Different genes control the development of different characteristics of an organism.d) Differences in the characteristics of different individuals of the same kind may be due to differences in:■ the genes they have inherited (genetic causes)■ the conditions in which they have developed (environmental causes)■ or a combination of both.

Chromosomes and Genes• Chromosomes, found in the cell nucleus, contain

many genes. • A gene is a section of DNA, which carries coding

for a particular protein. • Different genes control the development of

different characteristics of an organism. • Many genes are needed to carry all the genetic

information for a whole organism.

The Human• Humans have 23

pairs of chromosome, so 46 on total.

• For sexual reproduction only one from each pair is used.

Gametes• Gametes are also known as sex cells.• In a female this is the egg cell. In the

male this is called a sperm cell.• The nucleus of each gamete contains

chromosomes. There are 23 pairs for humans.

• Each chromosome carries thousands of genes.

Variation• In genetics, variation refers to an

individual that possesses characteristics different from the others of the same kind.

Causes of variation• Variation is caused by genes or by

environmental factors or by a combination of the two.

• Eye, hair and skin colour is caused by genes.

• Physical scars are due to environmental factors.

• Height and mass are a combination of both.

Types of variation• Continuous variation can vary gradually from

one extreme to another, for example height.• Categoric variation is usually caused by a

single gene and is one of a small number of possible choices, for example eye colour.

• Decide which type of variation the following are:– Eye colour– height– mass– skin colour– hair colour

B1.7.2 Reproductiona) There are two forms of reproduction:■ sexual reproduction – the joining (fusion) of male and female gametes. The mixture of the genetic information from two parents leads to variety in the offspring■ asexual reproduction – no fusion of gametes and only one individual is needed as the parent. There is no mixing of genetic information and so no genetic variation in the offspring. These genetically identical individuals are known as clones.b) New plants can be produced quickly and cheaply by taking cuttings from older plants. These new plants are genetically identical to the parent plant.

B1.7.2 Reproductionc) Modern cloning techniques include:■ tissue culture – using small groups of cells from part of a plant■ embryo transplants – splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers■ adult cell cloning – the nucleus is removed from an unfertilised egg cell. The nucleus from an adult body cell, eg a skin cell, is then inserted into the egg cell. An electric shock then causes the egg cell to begin to divide to form embryo cells. These embryo cells contain the same genetic information as the adult skin cell. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.

B1.7.2 Reproductiond) In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ using enzymes and transferred to cells of other organisms.e) Genes can also be transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.■ new genes can be transferred to crop plants■ crops that have had their genes modified in this way are called genetically modified crops (GM crops)■ examples of genetically modified crops include ones that are resistant to insect attack or to herbicides■ genetically modified crops generally show increased yields.f) Concerns about GM crops include the effect on populations of wild flowers and insects, and uncertainty about the effects of eating GM crops on human health.

Sexual Reproduction• Gametes required from male and

female parents.• Each gamete contains half the number

of chromosomes needed for offspring.• Large amount of variation.

Asexual reproduction• Only one parent is required, cells

divide without the need for male sperm.

• Offspring are identical to the parent, known as clones.

• No variation.

Asexual reproduction• Much faster than sexual reproduction.• Some plants reproduce asexually.• Cuttings can be taken from some

plants, this allows us to grow an identical plant from a stem or leaf.

Cuttings from Plants• Cuttings from plants produce identical copies.• Can only get a limited number of clones at

one time.• Damaging to mother plant

Tissue Culture• Using small groups of cells from part

of a plant

Embryo Transplant• Eggs are taken from a desirable female

(animals).• Sperm is taken from a desirable male.• These are combined in a dish.• A fertilised eggs is allowed to divide.• This is then split into multiple embryos.• Each of these embryos are put into less

valuable females.• Genetically identical offspring are born.

Adult Cell cloningAdult cell cloning involves several steps:1. The nucleus is removed from an unfertilised

egg cell and discarded2. The nucleus is removed from an adult body cell

and injected into the egg cell3. An electric shock is applied to make the egg cell

begin to divide to form an embryo4. While it is still a ball of cells, the embryo is

inserted into the womb of an adult female5. The embryo continues to grow and developThe new individual is genetically identical to the animal that donated the nucleus from one of its body cells.

Adult Cell cloning

Genetic Modification• Genetic modification, or GM for short, is

not the same as cloning. • Although cloning techniques are used in

genetic engineering, the two things should not be confused.

• This table shows some of the differences. Cloning Genetic

Modification

Produces exact copies Produces a unique set of genes

Genes copied within same species

Genes can be swapped across species

B1.8 Evolution

B1.8.1 Evolutiona) Darwin’s theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.b) The theory of evolution by natural selection was only gradually accepted because:■ the theory challenged the idea that God made all the animals and plants that live on Earth■ there was insufficient evidence at the time the theory was published to convince many scientists■ the mechanism of inheritance and variation was not known until 50 years after the theory was published.

B1.8.1 Evolution• c) Other theories, including that of Lamarck,

are based mainly on the idea that changes that occur in an organism during its lifetime can be inherited. We now know that in the vast majority of cases this type of inheritance cannot occur.

• d) 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 allow us to suggest relationships between organisms.

B1.8.1 Evolutione) Evolution occurs via natural selection:■ individual organisms within a particular species may show a wide range of variation because of differences in their genes■ individuals with characteristics most suited to the environment are more likely to survive to breed successfully■ the genes that have enabled these individuals to survive are then passed on to the next generation.f) Where new forms of a gene result from mutation there may be relatively rapid change in a species if the environment changes.

Classification• Classification – sorting organisms into

groups according to their characteristics.• We start with kingdoms, the main ones

are: plant; animal; and microbe.

Natural selection• Evolution happens due to natural selection.– Individual organisms within a particular

species may show a wide range of variation because of differences in their genes.

– Individuals with characteristics most suited to the environment are more likely to survive and breed successfully.

– The genes that have enabled these individuals to survive are then passed on to the next generation.

Darwin• Darwin’s theory of evolution by

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

Darwin’s Theory in a nutshell

• A Giraffe is born with a slightly longer neck due to mutation. (You could also say there is a variation in neck size, longer neck means better survival).

• That gives is a better chance of survival as it can get more food.

• The Giraffe survives and breeds.• This means the genes are passed on.• Giraffe’s child has a slightly longer

neck due to it’s genes.

The Problem with Darwin’s Theory

• The theory challenged that god made all the plants and animals that live on Earth.

• There was insufficient evidence at the time.

• The mechanism of inherence and variation was not known for 50 years after the theory was published.

Lamarck Theory• His theory centred on two ideas:– The law of use and disuse.– The law of inheritance of acquired

characteristics.

• His theory says that a characteristic which is used more and more by an organism becomes bigger and stronger. One that is not used disappears eventually. Any characteristic of an organism that is improved through use is passed to its offspring.

Lamarck’s Theory in a nutshell

• A swordfish used to have shorts swords.• The sword grew longer as each

swordfish used its sword more and more.

• Each time a swordfish reproduced, the longer sword was passed on to its offspring.

THIS IS AN INCORRECT THEORYBUT YOU NEED TO KNOW IT

Evolutionary trees