B1

Classification means grouping things by their features or characteristics. The more characteristics that are used to group similar organisms together, the more reliable is the classification. Small groups that are similar can be grouped in to larger groups. The groups that organisms are classified into are- Kingdom, Phylum, Class, order, family, genus, species. The 5 kingdoms are Anamalia, Plantae, Fungi, Prototoctista, Prokaryotae. viruses are not classified because scientists don't think they are living organisms because they have to use other cells to reproduce, and they show no other life processes, for example growth.
Anamalia don't have a cell wall or chlorophyll, they are multicellular and feed heterotrophically.
Plantae are multicellular, have a cell wall and chlorophyll and feed autotrophically
Fungi are multicellular, they are multicellular but have no chlorophyll and feed saprophytically.
Protoctista are mostly unicellular and have a nucleus in cell.
Prokarayotae are unicellular but have no nucleus.

Most cells contain a nucleus in which there are chromosomes. there are 2 copies of each chromosome in body cells- each copy has the same genes in the same order along its length (apart from the genes which determine sex). a gene is a short piece of DNA at a particular point on a chromosome- a gene codes for a characteristic, e.g. eye colour. A gene may come in different forms, called alleles, that produce different variations of the characteristics, e.g. different eye colours. Chromosomes of the same type are the same size and have the same genes in the same order. If the genes have the same allele on both chromosomes- the person is homozygous for these genes. different alleles of the same gene- the person is heterozygous for this gene.

Sometimes a characteristic is controlled by a single gene. This is called monohybrid inheritance. There are 2 types of alleles, these are recessive and dominant. A recessive allele only shows if the individual has two copies of the recessive allele. For example, the allele for blue eyes is recessive. You need two copies of the allele to have blue eyes. A dominant allele always shows, even if the individual only has one copy of the allele. For example, the allele for brown eyes is dominant. You only need one copy of the allele to have brown eyes (and two copies will still give you brown eyes).
Genetic disorders: Sickle cell disease is caused by having two copies of a recessive allele for the haemoglobin gene, which causes red blood cells to become sickle-shaped. people with the disease become short of breath and tire easily, have painful joints if the red blood cells get stuck in capillaries, and have a reduced blood flow. Cystic Fibrosis is caused by having two copies of a recessive allele for a cell membrane protein. This makes the mucus that lines tubes in the lungs, and other parts of the body much thicker and stickier than normal. this can increase the risk of lung infections, and prevent enzymes getting into the digestive system to break down food. Family pedigrees are diagrams which show the inheritance of a characteristic in a family. pedigree analysis helps predict the chance that someone has inherited a particular allele.

Different species are adapted to the environment they live in, organisms that live in extreme environments are specially adapted.
Deep sea hydrothermal organisms adaptions are: Little light- no eyes.
Extremely hot water- sense organs that detect dangerously high temperatures.
Acidic water, at high pressed and full of minerals- soft parts strengthened by iron scales.
Low oxygen concentration in water- haemoglobin to help take oxygen from the water.
Polar organisms adaptions are: White snow and ice- white fur to camouflage
Very cold in winter- to reduce the amount of heat leaving the body they may have- thick fur, extra fat below skin, bulky body and small ears.
Slippery ice- wide feet with rough soles to help grip the ice.
Key words:
Acquired characteristics- a characteristic that is changed by the environment
Continuous variation- where characteristics varies gradually and continuously between extremes - e.g. Height or weight.
Discontinuous variation- characteristics controlled by genes-e.g. Blood group, gender.
A normal distribution curve- has a bell shape, showing that the most common variation lies between two extremes, with fewer individuals having variations that are near to each extreme.