4 mechanisms for evolution 2012
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Mechanisms of Evolution: Power Point and associated vocabulary

Mechanisms of Evolution: Power Point and associated vocabulary

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4 mechanisms for evolution 2012 4 mechanisms for evolution 2012 Presentation Transcript

  • Allopatric speciation: The Grand Canyon is ageographical barrier separating the Albert and Kaibab squirrels
  •  Population – a group of organisms that interbreed Each population shares a gene pool (the different alleles present in the population) Each population has a relative frequency of each alleles, or the number of times the allele occurs in the gene pool. The frequency of alleles in a population tend not to change unless there is an outside force causing it
  •  Mutations are inheritable changes to the genotype of an organism Mutations occur randomly and spontaneously within a population Most mutations are harmful, but some are useful Mutations can affect allele frequency in a population by 1. Adding new alleles for a trait 2. Changing the amount of each allele present It can take a long time to eliminate a mutation and a long time for a new mutation to become prevalent
  •  There are 5 mechanisms that can change the allele frequencies in a population1. Mutation2. Migration3. Genetic Drift4. Non-random Mating5. Natural Selection
  •  Movement into and out of a population can change the allele frequency in a population’s gene pool Immigration can ADD individuals with variations to the population Emigration can REMOVE individuals with variations from a population. Can you think of large human immigrations and emigrations within the last 150 years? Many species encourage migration which can cause more gene flow which is the process of transferring genes among different populations
  •  Genetic drift is the random changes in allele frequency due to population size. In smaller populations the allele frequency can change more rapidly than in larger populations
  •  The founder effectoccurs when a fewindividuals from a largerpopulation colonize anew area. • Ex. Amish community. The allele frequencyof this population maydiffer from the largerpopulation because of thelimited number of individuals
  •  Havinga limited number of individuals can also impact mating. Non random mating can influence allele frequencies because: • Mates can be limited by geography • Mates can be chosen for their traits • Mates can be more closely related to one another
  •  Natural selection is process by which individual which are more fit for the environment survive and reproduce The interaction of populations and the environment results in changing allele frequencies There are 4 different types of natural selection: a. Stabilizing Selection b. Directional Selection c. Disruptive Selection d. Sexual Selection
  •  Stabilizingselection occurs when individuals with the average form of the trait are most fit for the environment and extreme traits are eliminated This is the most common form of selection and works in all populations at all times
  •  Lizard body size: • Large lizards are easily seen by predators, but smaller lizards cannot run as fast to escape the predators • Mid sized lizards are most fit in the environment, so they survive and reproduce more often, changing the allele frequencies in the population
  •  Directionalselection occurs when individuals with one extreme of variations are the most fit in the environment. Thiscauses a gradual shift in allele frequency to that extreme.
  •  Anteater tongue length: • Anteaters with long tongues are most fit because of the depth of the nests of the termites they eat.
  •  Disruptive selection occurs when both extremes of variations are the most fit There is selection against the middle variations Ex: Limpet shells • Dark limpets blend with bare rocks • Light limpets blend with barnacle covered rocks • Tan limpets are visible in both situations and get preyed upon by birds
  •  Sexual selection is the competition for mates within a population causing differences to occur in the allele frequencies of the 2 genders Matestend to be chosen for their phenotypes and females tend to choose the males.
  •  Ex: Peacocks • Male peacocks have large tail feathers that make it difficult to fly and escape from predators • Female peacocks choose males based on their tail feather length and fullness • Over time males with larger tail feathers reproduce more causing large tails to be selected for • Sexual Selection in Peacocks (3 min.)
  • In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage.
  •  Coevolutionary relationships mainly occur between plants and herbivorous insects and between plants and pollinating insects. Mutually beneficial relationship.
  • When organisms evolve similar (analagous) structures or functions even though their evolutionary ancestors are very dissimilar or unrelated. Example: The complex eyes of vertebrates, cephalopods (squid and octopus), cubozoan jellyfish, and arthropods (insects, spiders, crustaceans) evolved separately, but all perform the function ofhttp://images.sciencedaily.com/2009/06/0 vision90601182828-large.jpg http://jeffvrabel.files.wordpress.com/2011/08/wolf-spider-5-29-08- 7eyes.jpg
  •  Look at the cladogram at the right. What conclusions can be drawn about the relationship between humans and chimps?
  •  Note that this diagram is also a timeline. The older organism are located on the bottom of the tree. The four descendents at the top of the tree are DIFFERENT species. This is called SPECIATION.
  •  Branches on the tree represent SPECIATION, the formation of a new species. The event that causes the speciation is shown as the fork of the “V”.
  •  Did humans evolve from chimps? No What familial relationship is a good description of the relationship between chimps and humans? Distant Cousins Are humans more highly evolved than chimps? NO- since the lineage is split, each species has evolved unique traits.
  • With 98.4% similar geneticsequences chimpanzees are both alink to Kingdom Animalia and ourkin. Anima: James Balog images used with permission. http://www.jamesbalog.com/