B14

• Variation is the differences in characteristics of individuals in a population
• differences in characterisitcs of same species may be due to: differences in genes they have inherited, conditions in which they have developed, combination of both genetic and environmental causes
• genes are most important factor in controll appearance of individual
• plants may be affected by lack of light, nutrients or space to grow
• if plants are deprived of nutrients a plant cannot grow as well as other plants that have sames genes but grown in better conditions
• human development may be affected during pregnancy, if the mother smokes or drinks, baby may have low birthweight
• once animals are born, too much or too little food can alter their characteristics
• selective breeding is process where humans breed plants and animals for their desired characteristics and has to be repeated over many successive generations to get new breed
• selective breed is used to select features like: disease resistance in food crops or garden plants, animals that produce more meat or milk, domestic dogs and farm animals with gentle nature and large,unusual brightly coloured or heavily scented flowers
• DISADVS OF SELECTIVE BREED: reduces number of alleles in population, less variation, new disease or climate change could destroy whole population and inbreeding can lead to inherited defects
• ADULT CELL CLONING STEP 1: The nucleus of an adult cell, such as a skin cell, replaces the nucleus of an egg cell
• ADULT CELL CLONING STEP 2: The new cell is given an electric shock that causes it to start to divide
• ADULT CELL CLONING STEP 3: The ball of cells is called an embryo
• ADULT CELL CLONING STEP 4:The embryo is genetically identical to the adult skin cell
• ADULT CELL CLONING STEP 5: Once the embryo has developed into a ball of cells, it is inserted into the womb of a host mother
• GENETIC ENGINEERING: A gene for a desired characteristic is 'cut out' of the chromosome of an organism using an enzyme. The gene is then inserted into the chromosome of another organism. A vector (carrier) such as a plasmid or virus may be used to transfer the gene
• In genetic engineering, the new gene is often inserted into an organism of the same species to give it a 'desired' characteristic
• Crops with genes are called genetically modified (GM) crop plants
• GM crops may make their own pesticide, or be herbicide-resistant, and usually have increased yields
• clones are individuals that are genetically identical to their parents
• tissue culture is process of taking small groups of cells form part of plant and growing them under special conditions. A mass of identicall cells form called callus. each callus cell can be grown into new plant
• plants can be cloned by taking cuttings and growing them or tissue culture
• Embryo transplants are used to clone animals
• In embryo transplants, an embryo with unspecialised cell is split into smaller groups of cells. each group of genetically identical cells is transplanted into host animal to allow to develop into new individual
• PROCESS OF CLONING STEP 1: divide each embryo into several individual cells
• PROCESS OF CLONING STEP 2: each cell grows into an identical embryo in lab
• PROCESS OF CLONING STEP 3: transfer embryos into their host mothers who have been given hormones ready for pregnancy
• PROCESS OF CLONING STEP 4: identical clones are born and not biologically related to their host mothers
• the organims with characteristics most suited to environment will survive so fittest organisms will survive
• organism that survive are more likely to breed successfully and pass on these genes that enable them to survive to their offspring
• sometimes mutation leads to new phenotype. if new phenotype is suited to an environmental change, it can lead to rapid change in species
• natural selection results in process of adaptation so over generations those features that are better adapted to enviroment become more common
• new species may evolve if 1 population of species changes so much they can no longer breed with another population to produce fertile offspring