1. Chapter 6 Ecology and Evolution

2. Case Study: Inadvertent Evolution Bighorn Sheep: Ovis canadensis; have the ability to balance on steep ledges Males can weigh 180 lbs; their horns are collected as trophies, which caused populations to reduce by 90% This hunting has taken the largest, strongest males out of the population How do you think the population has changed?

4. Humans Affect Evolution Global warming Hunting Fishing Pollution Deforestation How do these affect populations of organisms?

5. Chapter 6.1: What is Evolution Evolution: Change in a population overtime Change can be large or small – Examples: bighorn sheep horn size decreases over time Whales lost their back legs over time (still have a pelvis) Evolution occurs on a genetic level Genes control physical traits that are either good or bad for a specific environment

8. Evolution is Genetic Genes are made of DNA – DNA codes for specific proteins A gene can have two or more forms (alleles) for a given trait Genotype: the genetic make-up of an individual Phenotype: the physical traits of an individual

11. Descent with Modification Charles Darwin hypothesized that offspring (descendants) change from their parents over many generations This occurs because of natural selection: the environment dictates evolution based on certain traits (adaptations) POPULATIONS evolve; individuals do NOT – DNA does not change in an organism, DNA is selected for or against

13. Chapter 6.2: Mechanisms of Evolution There are four key influences of evolution: – Mutation – Natural Selection – Genetic Drift – Gene Flow Mutation is the raw material for evolution A change in DNA CAN change an entire gene, but sometimes it has no affect

16. Genetic Differences Organisms differ genetically in each species Differences are due to: – Mutations – Recombination Recombination: rearrangement of alleles between parent and offspring (occurs in Meiosis I)

18. Natural Selection The process of natural selection INCREASES alleles that are advantageous These alleles are then selected for in one of three ways: – Directional selection: one extreme is favored – Stabilizing selection: intermediates are favored – Disruptive selection: both extremes are favored

21. Genetic Drift is Random Genetic drift: a mechanism that can cause allele frequencies to change CHANCE events affect genetic drift Usually, only small populations are affected over a short period of time Example: – A wildflower population is severely altered when a moose crushes 40% of it

24. Gene Flow Gene flow: alleles move from one population to another Gene flow usually occurs because of emigration and immigration This can introduce new alleles into a population, but it can also take alleles out of a population

27. Chapter 6.3: Adaptive Evolution Adaptations: characteristics of an organism that INCREASES its ability to survive and reproduce in a particular environment – Example: white fur on a polar bear, beak size for finches, trunk on an elephant, etc Adaptations result directly from genes Natural selection directly causes adaptive evolution

29. Adaptive Evolution can be Quick Depending on the organism and it’s generation time, adaptations can drive evolution quickly Bacteria populations can develop antibiotic resistance in a matter of days Insects can become immune to insecticides in a matter of weeks to months

31. Adaptations are NOT Perfect Just because an adaptation occurs, does not mean it’s a perfect match for the environment This is sometimes caused by gene flow, but not always Most likely, the environment surrounding the organism is constantly changing, so the organisms need to constantly adapt

32. Chapter 6.4: Evolutionary History of Life The diversity of life has resulted in speciation Adaptations to different environments has developed new species Species: a group of organisms with similar characteristics that HAVE the ability to interbreed Speciation usually occurs when two populations are cut off from each other

34. Mass Extinction & Adaptive Radiation In earth’s history, there have been a few instances of mass extinction of life Because of extinctions, large holes were left in particular habitats and niches that needed to be filled Adaptive Radiation: a group of organisms forms many different species to fill empty habitats and niches

37. Chapter 6.5: Ecology & Evolution Ecology and evolution are completely intertwined Different ecological interactions can shape evolutionary patterns through adaptations – Predator/prey interactions – Red queen hypothesis – Competition

39. Ecology & Evolution Evolution can also alter ecological interactions – Predator/prey interactions – Red queen hypothesis – Competition Adaptive radiation can affect the physical environments, affecting other species as well As populations adapt, they can also change their own environment, causing other populations to adapt as well

41. Case Study: Revisited Humans inadvertently caused bignorn sheep to adapt to being hunted (smaller average horn size) How else have humans affected evolution? – Antibiotic resistance in bacteria – Fish size – Fox fur color