Origin of Species Chapter 22 Types of Evolution

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Origin of Species Chapter 22

Origin of Species Chapter 22

Types of Evolution • Microevolution – genetic changes in a populations gene pool from

Types of Evolution • Microevolution – genetic changes in a populations gene pool from generation to generation. – Hardy-Weinberg and natural selection – Can form two species if gene pools diverge enough • Macroevolution – patterns of changes in groups of species over long periods of time. – Phylogeny – relationships among different species

What is a species (spp. )? • Biological species concept – Organisms of the

What is a species (spp. )? • Biological species concept – Organisms of the same spp. can interbreed to produce viable and fertile offspring only w/ their own spp. Ernst Mayr • Other concepts that emphasize similarities w/in a spp. • Morphological Spp. Concept – orangizes spp. by body shape & other structural features • Ecological species concept – categorizes species based on its ecological niche – role in the environment – Can be used for asexual reproduction • Phylogenetic species concept – determines a species based on molecular sequences – Usually used to compare sister species – species that are morphologically similar

Formation of a new species • Isolation – separation of gene pools • Geographic

Formation of a new species • Isolation – separation of gene pools • Geographic Isolation – geographic barrier between organisms in a population that prevents them from breeding – Isolates gene pools • Reproductive Isolation – inability of organisms to produce fertile offspring • Adaptive Radiation – many species form rapidly from one common ancestral species

Allopatric Speciation • geographic barrier prevents the interbreeding of two populations – Earthquake, tsunami,

Allopatric Speciation • geographic barrier prevents the interbreeding of two populations – Earthquake, tsunami, lava flow, etc. – Island colonization (remote area) • Once the two populations diverge through natural selection over time they may not be able to reproduce if brought back together Ground squirrels in the Grand Canyon

Sympatric speciation – new species formation without a geographic barrier – Balanced polymorphism –

Sympatric speciation – new species formation without a geographic barrier – Balanced polymorphism – physical variations within a species one has selective advantage • If one type is selected against only the remaining can mate…new gene pool – Polyploidy – possession of more than the normal diploid number of chromosomes – Autopolyploid: 2 n doubles to 4 n due to a translocation, the 2 n & 4 n organisms can’t reproduce – Allopolyploid: previously sterile hybrid becomes fertile (usually plants) new spp. forms

Hybridization • occurs when two species normally separated by a geographic boundary mate and

Hybridization • occurs when two species normally separated by a geographic boundary mate and produce offspring that is fertile. – New offspring may become own species – Hybrid Zones sometimes remain stable if original spp. can’t survive in hybrid zone conditions

Adaptive Radiation • Many species are formed from one ancestral type when the original

Adaptive Radiation • Many species are formed from one ancestral type when the original species is introduced or migrates to an uncolonized area – Usually occurs after a mass extinction when there are new Ecological Niches to colonize

Reproductive Isolation • Pre-zygotic – occurs before fertilization – pg 419 -420 – Habitat

Reproductive Isolation • Pre-zygotic – occurs before fertilization – pg 419 -420 – Habitat – no encounter – Temporal – breeding occurs during different times of the day, seasons, or year – Behavioral – mating rituals are not the same – Mechanical – male and female parts are not compatible – Gametic - male and female gametes do not recognize each other • Post-zygotic – occurs after fertilization – Hybrid inviability – offspring doesn’t survive or is very weak – Hybrid sterility – offspring is produced but infertile – Hybrid breakdown – 1 st generation is fertile, but when mated with each other the 2 nd generation is sterile

Patterns of Evolution • Convergent – species become more and more similar due to

Patterns of Evolution • Convergent – species become more and more similar due to environment – Orca and Shark • Divergent – species become more and more different – Okapi and Giraffe • Parallel – 2 related species follow similar pattern of changes – Leaf structure of plants • Coevolution – one species changes and causes a change in the other – dependency – Hummingbird and flowers

Rates of Evolution • Gradualism – slow accumulated changes over long periods of time

Rates of Evolution • Gradualism – slow accumulated changes over long periods of time • Punctuated Equilibrium – rapid change with periods of no change