genes

• what is evolution


  The theory that all species living today gradually developed from species that existed in the past
• What does the fossil record show

  Shows us that animals have existed in the past which have now become extinct
• what are fossils 


  fossils are the remains or traces of animals or plants that lived many years ago
• What is the concept of natural selection

  Only the best adapted animals will survive to pass on their genes and weaker animals will die out
• organisms with the best adaptations survive and reproduce and pass on their genes and continue to pass it on to the next generation and over a period of time the best adaptations continue to be passed on which can lead to a new species being formed
• Weaker organisms die out and do not pass on their genes
• what is an example of natural selection


  giraffes with long necks use them to eat from trees but giraffes with smaller necks would not be able to eat and would die
• What happens when a specie goes extinct


  All of the species dies out
• What can extinction be caused by

  Changes to the environment

  Destruction of habitat

  New diseases

  Introduction of new predators

  Increased competition
• what is reduction in biodiversity 


  when a species becomes extinct the variety of species within an ecosystem is reduced
• What is biodiversity

  A measure of the variety of all the different species of organisms on earth or within a particular ecosystem
• Why is biodiversity vital for maintaining populations

  The greater the variation within a species the more likely some members of the population will survive environmental changes reducing the likelihood of the species going extinct
• what are endangered species

  species which are at risk of extinction
• What are the three ways scientists are trying to prevent extinction from happening

  Conservation

  Captive breeding

  Gene banks
• what is conservation?


  conservation means protecting a natural environment to ensure habitats are not lost
• what else does conservation do other then reducing extinction

  reduces disruption to food chains and food webs

  makes it possible for medicinal plant species to be discovered
• what is captive breeding?


  Captive breeding means breeding animals in human-controlled environments which aims to create a stable population of a species and gradually introduce the species back into nature
• what are the problems with captive breeding

  maintaining genetic diversity can be difficult

  organisms born in captivity may not be suitable for release in the wild
• what are gene banks?

  gene banks store genetic samples from different species
• What are the different types of gene banks

  Seed banks-dried seeds of plants are stored at low temperatures

  tissue banks-buds and other cells from plants are stored

  cryobanks-a seed or embryo stored at very low temperatures

  pollen banks-pollen grains are stored
• How does biodiversity benefit humans?

  Provides useful products and services for humans for example the plants in rainforests are very useful and maintaining biodiversity ensures we have a rich food supply
• Your inherited characteristics come from your parents through genetic material stored in the nucleus of your cells.
• What is this material called?

  This material is a chemical called DNA, which contains all the information needed to make an organism
• Where are chromosomes found?

  In the nucleus
• What are chromosomes?


  Chromosomes are long strands of DNA which hold many genes humans have 46 of these in the nucleus of cells
• What are genes?


  genes are a section of DNA which hold the information for a particular characteristic
• How is genetic material inherited?

  The 46 chromosomes are arranged into 23 pairs. One copy of a chromosome of each pair comes from your mother and the other comes from your father during fertilisation the egg and sperm cells joint together when the nuclei join the chromosomes up producing an embryo with 46 chromosomes
• What is mutation?


  A change in DNA
• What happens if a change occurs in a gene?

  It can affect for organisms characteristics, but your body normally detect these changes and tries to mend them if undetected they can lead to disease
• What happens if a mutation occurs in a gamete cell?

  The altered form of DNA maybe passed onto the organisms offspring
• What are the three main features of DNA?

  It is made up of two strands

  The strands of joint together by four different chemicals called DNA bases

  The strands are twisted together to form a double helix shape
• what are different forms of the same gene called?

  Alleles
• What are dominant alleles?

  Alleles which will always produce a characteristic in an organism
• What are recessive alleles?


  Alleles that are only expressed in organism if there are two copies
• What is genetic modification?

  The process which scientists can use in order to alter the genes of an organism
• What are examples of genetic modification?

  Altering cotton to produce higher yields and altering bacteria genes to produce medicines
• What did Charles Darwin and Alfred Wallace come up with?

  The theory of evolution by natural selection
• What is the process by which organisms evolve known as?

  Natural selection
• How is a gene different to a chromosome

  A gene is a section of a chromosome which hold the information for a particular characteristic