Topic 6 - Variation and Evolution Flashcards
Define the term Variation (1)
All the differences in the characteristics of individuals in a population
Define and give an example of genetic variation
Genetic variation (combination of genes from two parents)
e.g eye colour , blood group, inherited disorders
Define and give an example of environmental variation
variation caused by environmental factors
e.g yellow leaves, how tanned you are
Define Mutation
Changes to the sequence of bases in DNA
When do scientists believe life on Earth first began
3,000,000 years ago
What was Charles Darwin’s Theory? “survival of the fittest”
Organisms with the most suitable characteristics, for the environment, would be more successful competitors and would be more likely to survive
Define Natural Selection
The organisms with the most suitable characteristics are more likely to survive and reproduce, beneficial alleles are then passed on to the offspring
Define Evolution
A change in the inherited characteristics of a population over time through a process of natural selection
Explain 3 ways why Charles Darwin’s book “the origin of the species” 1859 was controversial
• It went against religious beliefs about how life on Earth first developed (God)
• There wasn’t enough evidence to convince scientists
• He didn’t have any explanation for why new characteristics appeared or how they were passed on to offspring
Define Selective breeding
When humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population
What is the negative of selective breeding ?
• Reduction in the gene pool (number of different alleles)
Explain the selective breeding process (4)
1) From your existing stock select the ones which have the characteristics you are after
2) Breed them with eachother
3) Select the best of the offspring and breed them together
4) Continue this process over several generations, as the desirable trait will get stronger and stronger
5) Eventyally all offspring will have the characteristic
Explain what a gene is and it’s role
Genes are sections of DNA on a chromosome. Each gene codes for the amino acid sequence of a specific protein
What are the benefits of GM crops (genetically modified)
produce a greater yield and resistant to disease or insect attack
Explain the main steps in genetic engineering
1) First we identify the gene we want to transfer
2) Use enzymes to isolate the gene
3) transfer gene into a small circle of DNA (plasmids)
4) Transfer the desired gene into the cells of the targeted organism
What should be done if genetic engineering is done in animals
If done in animals they should do it at and early embryo stage, this is to make sure all of the cells receive the transferred gene and then develop with characteristics we want
What are the two ways you can clone plants
Cuttings
Tissue Culture
What is the process of cloning plants by “cuttings” (small number)
A small piece of plant is removed and the end is dipped in rooting powder (contains plant hormones encourages plants to develop roots)
• genetically identical clones of the starter plant is produced
What is the process of cloning plants by tissue culture
• Take a plant that we want to clone and divide the plant into hundreds of tiny pieces
• Each piece contains a small number of cells
• Small groups of cells are then incubated with plant hormones
What should the conditions be when cloning plants
Conditions should be sterile because we do not want to introduce any microorganisms
What are the two ways to clone animals
Embryo transplants
Adult Cell cloning
Explain the process of Embryo Transplants
• We start with the sperm and egg cell from an animal with characteristics we want
• Fertilisation produces a fertilised egg
• Allow the fertilised egg to develop to an early stage embryo
• use a glass rod to split this embryo into two
• Transplant embryos into host mothers
• When the animals are born we get two identical offspring
What is the problem with embryo transplants (animal cloning)
Because we start with the sperm and the egg we cannot be certain that the offspring will have the characteristics we want
Explain the process of Adult Cell Cloning
• Start by removing a cell from the adult we want to clone.
• Then remove the nucleus
• Take an unfertilised egg cell from the same species
• Then removed nucleus from unfertilised egg and throw it away
• Now insert the nucleus from original adult body cell into empty egg cell
• Then give egg cell and electric shock (egg divide to form an embryo)
• The embryo cell contains same genetic information as the adult cell
• Once embryo has developed into a ball of cells it’s inserted into the womb of an adult female to continue developing.
