May 07, 2015 Main Points of Natural Selection 1. Living things over-reproduce • More individuals are born than survive 2. There is variation in traits among individuals • Each living thing does not appear exactly like all the others 3. There is a struggle to survive, competition for resources • There are more living things than there are resources • Organisms compete with each other for resources and survival 4. Natural Selection is always taking place. - Individuals with traits that increase fitness have more offspring than those without those traits • Fitness: organism's ability to survive and produce successful offspring
Transcript
May 07, 2015
Main Points of Natural Selection
1. Living things over-reproduce• More individuals are born than survive
2. There is variation in traits among individuals• Each living thing does not appear exactly like all the others
3. There is a struggle to survive, competition for resources• There are more living things than there are resources• Organisms compete with each other for resources and survival
4. Natural Selection is always taking place. - Individuals with traits that increase fitness have more offspring than those without
those traits• Fitness: organism's ability to survive and produce successful offspring
• Species: group of living things that reproduce with others of the same species and produce fertile offspring
Speciation
• Speciation: the process by which new species evolve from old oneso Speciation commonly occurs when members of a species have
been separated
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Alleles, Populations and Gene Pools
A group of individuals of the same species = a population
Assume that each member of the population could potentially mate and reproduce with any other member of the population, then:• Each member of the population has two
alleles for every trait• The total number of alleles for each trait in a
population = the gene pool
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Gene Pools and Gene FlowAs long as members of a population have the potential to reproduce with any other individual, there is gene flow within the population• Gene flow may happen between populations as
well.
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Separation of Species
• New species may form due to:o Formation of barriers (rivers, oceans, mountains, glaciers, lava flows)
• Animals of the same species find themselves living in different environments
• This causes reproductive isolation, or the separation of population so that species cannot interbreed
• Natural Selection will work separately on each group
• With different gene pools, different adaptations can appear in each group that are not passed along during mating
• This increases the differences between the groups and their gene pools become more dissimilaro If this occurs for a long period of time, the gene pools will be too different
to allow the organisms to ever interbreed, thus creating two different species• EX: species of finches on Galapagos Islands• Each species of finch had a different beak shape to suit the food on their
islando Thick beaks for eating seedso Small beaks for eating insects
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Evidence of EvolutionFossils
• Fossils are preserved remains/impressions of ancient organisms
• Fossils are found in sedimentary rockso Position of fossils in rock layers reveal the relative age of the organism
• Fossil record: time line of fossil appearances in rock layers, marking the passing of geological timeo Some fossils are not preserved well and some organisms do not leave
fossils at all - this accounts for gaps in the fossil recordo The fossil record provides information about:
• The age of the Earth• Changes in Earth• Evolution of species• Earth’s climate and geography
• Homologous Structures are traits that have similar structures but different functions in different specieso EX: Flippers, hands, bat wings, and bird wings all function
differently, yet are made up of the same group of bones!
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Vestigial Structures
• Vestigial Structures are structures that are reduced in size and often unused
o Historical remnants of structures important in ancestors• EX: whales of today lack hindlimbs, yet have vestiges of the pelvis and leg bones of their 4-footed terrestrial ancestors
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Comparative Embryology
• Comparison of structures that appear during the development of different organisms
• Closely related organisms often have similar stages in embryonic development
• Evidence that vertebrates evolved from a COMMON ANCESTORAll vertebrates (fishes, frogs, snakes, birds, apes) have gill pouches/slits on sides of throat during embryonic stage
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Comparative Biochemistry (molecular biology)• Common genetic code shared by all species• Evolutionary relationships among species leave signs in DNA/proteins
(genes/gene products)• If 2 species have genes/proteins with sequences that match closely,
sequences must have been copied from common ancestor• EX:
o Cytochrome C is a protein used in respiration by all organismso ATP is an energy molecule for all living things
o All organisms use DNA and RNA to transmit genetic info
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Biogeography• Biogeography is the
study of the distribution of different species on Earth
o Suggested to Darwin that organisms evolved from ancestral forms
• Galapagos animals resembled species of South American mainland more than animals on similar but distant islands
• EX:o Tropical animals of
South America more closely related to species in African deserts than to species in South American tropics
