evidence for evolution

• fossils are proof that evolution has occurred and that organisms have changed over time
• fossils are the remains of dead organisms from the past that are found in rocks
• fossils can be formed when hard bones from animals are buried in sedimentary rock
• fossils can be formed when conditions needed to decay (by microorganisms) are absent , e.g the fossil is covered by ice so the bones can be quickly formed
• fossil records are the evidence of past life forms and are found in rocks and sediments
• fossil records show how bones change over time
• fossil records show how simpler built organisms are found in the oldest soil layers
• fossil records show how more complex organisms are found in recent soil layers
• fossil records support the idea that forms have evolved over time
• define fossils

  the remains of an organism that died long ago
• define evolution

  the process in which living organisms develop over time
• natural selection is the process by which individuals with certain inherited characteristics are more likely to survive and reproduce
• survival of the fittest is the idea that the best adapted individuals will survive and reproduce
• variation is the differences in the characteristics of individuals in a population, due to genetic differences
• what is the difference between survival of the fittest and the weakest?

  Survival of the fittest: is where organisms best adapted to their environment are most likely to survive and reproduce. The weakest: is where Organisms less adapted to their environment are more likely to struggle to survive and reproduce.
• what is the advantage of the survival of the fittest?

  Adaptation and more reproduction
• disadvantage of survival of the weakest?

  Decreased genetic diversity and less reproduction
• how are fossils less found nowadays?

  because of over collection

  less burial of dead organisms

  not all organisms form fossils

  fossils can rot into dust overtime
• natural selection is the process of the best adapted animals to reproduce and survive
• variation is a specific select of an organism that is different from the other members of the same species
• define natural selection

  natural selection is a process where the best adapted animals survive and are chosen/able to reproduce
• define variation

  variation is a specific selection of an organism that is different from the same species
• what will happen if a giraffe has a short neck and cant reach the branch to eat?

  the giraffe will Struggle to eat and survive , therefore the giraffe will die and will be unable to reproduce to its offspring
• what is offspring?

  Children of animals
• define offspring

  offspring the children of animals
• lions prey for giraffes so explain how does this have a risk and an impact on the giraffe population?

  the giraffe population will Decrease because of lions hunting them down to eat , which will also make less giraffes reproduce so it will make them more likely to become extinct
• mutation is a change in the DNA sequence of a gene that can lead to a change in the amino acid sequence of a protein
• define mutation

  mutation is when there is a change in the dna sequence of a gene
• toms mother has blue eyes , and the blue eye alleles are recessive , toms father has brown eyes , and the brown eye alleles are dominant,

  i) explain what is meant by recessive

  recessive means the gene is less dominant
• ii) what is an allele?

  different versions of the same genes
• iii) toms mothers genotype is Bb

  so what is toms genotype?

  homozygous - bb
• write down the pair of sex chromosomes that are in a body cell of a male

  XY
• write down the pair of sex chromosomes that are in a body cell of a female

  XX