AS BIology Evolution

Variation
1. variation is the difference between individuals
  1. Intraspecific variation is between species
  2. Interspecific variation is between different species for example different masses of different types of birds
2. Variation can be both continuous and discontinuous , continuous is when the variation is within a range and discontinuous is when there are two or more distinct catagories
  1. Discontinuous could be sex/blood group in animals , colour / seed shape in plants or antibiotic resistance/pigment production in microorganisms
  2. Continuous could be milk yield/mass in animals, number of leaves/mass in plants and width/length in microorganisms
3. Can be caused by genetic/ environmental factors
  1. Different species have different genes, same species have same genes but different alleles . These make up the genotype which results in a varying phenotype. (characteristics). Genetic variation is inherited
  2. Environmental factors such as climate also have an effect like location affects accent and lifestyle/culture with peircings
  3. Genetic variation is inherited but environmental factors can influence them like height is inherited but also affected by health
Adapatations
1. making an organism well suited to its environment , adaptations make chances of survival increase and reproduction more likely to be successful
2. Behavioural adaptations are things such as possums playing dead to avoid being killed. Scorpions dance to attract the right mate for reproduction
3. Physiological adaptations are processes that increase the chance of survival such as hibernating to conserve energy and bacteria producing antibodies to kill other species and reduce competition
4. Anatomical adaptations are physical things like streamlined otters to improve speed in swimming and whales having thick blubber layers to insulate them in their cold environments
The theories of evolution
1. Darwin's theory of natural selection
  1. Observations and theory
    1. More offspring are produced than survive , characteristics between species show variation and these can passed on as the best adapted are more likely to survive
    2. Phenotypes variation allows some individuals in species to be better adapted from predators, disease and competition. They are more likely to survive and pass on their better genes to the next generation and over time adaptations become more common in species
  2. Evolution leads to speciation , the formation of a new species. It happens when one species evolves so much that it becomes unable to produce fertile offspring with the rest of its species
    1. Darwin's finches - 14 species from the Galapagos islands , all found to have a common ancestor , became isolated on the islands and adapted to the food sources there , changing their beak type and resulting in them being unable to mate with each other to produce fertile offspring
2. Evidence to support evolution
  1. Fossil record evidence can be chronologically ordered into showing gradual changes through species like in the size of horses hoof's
  2. DNA evidence shows evolution is caused by gradual changes in base sequences of organisms DNA. The closer the related a species are, the more similar the DNA. Also applies for species that have evolved recently like humans and chimps
  3. Molecular evidence such as comparisons between amino acid sequences in proteins and antibodies
3. Resistance to antibiotics
  1. MRSA is resistant to antibiotic methicillin because of genetic mutations through natural selection. (Only the mutated resistant ones will survive to reproduce more and pass on the alleles
  2. Infections become harder to treat and it takes a long time to produce and invent new antibiotics that bacteria isn't resistant to
4. Resistance to pesticides
  1. Mosquito's have developed resistance to DDT through natural selection working in the same way as the genetic mutations in bacteria in antibiotic resistance.
  2. Crop infestations become harder to overcome , crops get destroyed and disease is spread much quicker. In some cases populations become resistant to pesticides which again will take a lot of money and time to solve

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AS BIology Evolution

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	Created by Megan Tarbuck over 9 years ago