B1 Revision

Topic 1 - Variety of Life, Adaptation and Competition

Morphological features ( Structure or appearance) – Gives the 5 Kingdoms.

All Living Organisms

Animals

BacteriaFungi

Single celled organisms

Plants

DNA analysis – Gives the 3 Domains. This is the preferred method.

All Living Organisms

Bacteria

Ancient single celled

organisms

All organisms with a nucleus

Living Organisms

Plants

Flowering plants

Non- flowering plants

Living Organisms

Animals

Vertebrates Invertebrates

Living Organisms

Microorganisms (microbes)

Algae (single celled organisms)

Bacteria Fungi

Classification of a lion

• kingdom – animal (animaila)• phylum – vertebrate (chordata)• class – mammal (mammalia)• order – carnivorous (Carnivora)• family – cat (Felidae)• genus - big cat (Panthera)• species – lion (leo)

• Panthera leo

Adaptations

Population

Predator-prey cycle

Topic 2 - InheritanceChromosomes (DNA) are stored in the nucleus.

Humans have 46 chromosomes (or 23 pairs).

Humans have a pair of sex chromosomes.Female = XXMale = XY

DNA• DNA contains coded information which determines the sequence of

amino acids which make up the different types of proteins produced in the cell.

• The protein will then be different which will affect the functioning or characteristics of the organism.

Genetic Profiling - is the analysis of an organism’s DNA.

• Human body cells have 46 chromosomes.

• Human sex cells (gametes) have 23 chromosomes.

• The number of chromosomes in the egg and sperm are half the number in a normal cell.

• This is so that when they join together in fertilisation the offspring will have the correct number of chromosomes. (inheritance of sex)

Sperm + Egg = Fertilised egg (zygote)

23 23 46

Gregor Mendel • Mendel began the study of genetics. He investigated the inheritance of

height in pea plants. TTTt

T = Tall allele (dominant) t = Short allele (recessive)

Ratio, probability, percentage.

GM Crops - Transferring genes artificially from one species to another.

Topic 3 – Variation and Evolution• Variation means the differences between individuals of the same

species. Variations are the result of :• Genetic information (genes) • The environment,

• Types of variation: • Continuous variation is controlled by more than one set of genes. When described using a graph it shows a normal distribution, e.g. height.

• Discontinuous variation is usually controlled by one set of genes. When graphed it shows distinct groups, e.g. blood groups.

Asexual Reproduction• Only needs one parent • Produces clones

• No variation • Genetically identical to the parent

Sexual Reproduction• Needs two parents

• Leads to variation • Genetically different to the parent

Mutation - is a change in the DNA molecule resulting in a new gene. This can result in a new characteristic that may be passed onto the next generation.

• Ionising radiation,• X-rays • Ultra violet radiation from the sun, • Some toxic chemicals (mutagens).

Cystic Fibrosis

Gene therapy

Evolution - is the gradual change in species over time, resulting in the formation of new species, and the extinction of others. • The mechanism for evolution is natural selection • Natural selection – • 1. There is variation in a population (from a mutation)• 2. There is competition for survival. • 3. Some individuals have a characteristic that gives them an advantage. (E.g.

ability to run faster). • 4. The individuals that survive are more likely to reproduce and pass the gene

(that controls the characteristic giving them the advantage) on to their offspring.• 5. Over a long period of time the advantageous gene will become more common

in the population, (provided the environment does not change). • Species that don’t have much variation are less likely to adapt quickly when the

environment changes and will become extinct.

Unit 4 – Response and Regulation• Each sense organ is made up of special cells called receptors. • The receptors can respond to a certain stimulus. • The receptors collect information from out surroundings and pass the

information as electrical impulses along nerves to the central nervous system. • The central nervous system (the brain or spinal cord) can then store the

information or decide on a reaction.

Plant Senses•A tropisms is the growth of a plant towards a light source or

in response to a source of gravity. •Phototropism: response to light •Gravitropism: response to gravity •Growth towards a stimulus is a positive tropism • and growth away is a negative tropism. • Plant hormones regulate growth and other functions in plant cells.

Homeostasis -means keeping the internal environment constant

• Hormones are chemical messengers that control many body functions. They are produced by glands and carried by the blood. Hormones are proteins.

• Water content • Waste chemicals • Body temperature • Glucose levels

The Skin

Topic 5 – Monitoring the Environment

Pollution in rivers and streams can be measured using: • Changes in pH levels• Changes in oxygen levels • Indicator species

• Lichen can be used as indicator species for air pollution. Lichens are sensitive to sulphur dioxide gas

Bioaccumulation• The further along a food chain an organism is, the more chemicals

accumulate in its tissues. • The scientific name for this is bioaccumulation. • The organism at the end of a food chain will receive a toxic dose that has

harmful effects, e.g. reducing fertility or death.

• Explanation – (QWC question model answer) • Fertilisers containing nitrates and phosphates are washed into streams, rivers, ponds and the sea.• Nitrates and phosphates cause an increase in the growth of water plants or algal blooms. • Some plants start dying because there is increased competition for light. • Decomposing bacteria decompose (rot) the dead plants. • The number of decomposing bacteria increases. • The decomposing bacteria use up the oxygen in the water for respiration. • There is less oxygen in the water. • Animals, such as fish, die because there is not enough oxygen in the water.

Carbon Cycle

The Nitrogen Cycle

• Living organisms need nitrogen to make proteins. • 79% of the air is nitrogen, but plants and animals can’t use nitrogen• Nitrogen must be changed into nitrates before plants can use it.Nitrates can be absorbed by plant roots and used to make proteins. This protein then becomes food for animals as it is passed on along food chains

• When a plant or animal dies,• • Soil bacteria and fungi act as decomposers, • • They convert protein (and urea from urine) into ammonia,• • The ammonia is then converted to nitrates in a process

called • nitrification.• • Nitrifying bacteria carry out nitrification.• • The nitrates arethen absorbed (taken up) by plant roots.• • The nitrates are used to make amino acids.• • The amino acids are then used to make new proteins.

Topic 6 - Health