Evolution and Biogeograhy June 20, 2006 Lecturer: Meg Grantham

Adaptive Features of Organisms  Ancestral descent with modification – something arises that makes organism better equipped to survive.  Natural Selection – features allow organism to survive to reproduce.

Macroevolution: the origin of new taxonomic groups  Speciation: the origin of new species  1- Anagenesis (phyletic evolution): accumulation of heritable changes   2- Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity)

What is a species?  Biological species concept (Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations)

Speciation  Morphological species – determined by appearance  Biological species – the largest unit of a population in which gene flow is possible without artificial means

Reproductive Isolation (isolation of gene pools), I  Prezygotic barriers: impede mating between species or hinder the fertilization of the ova  Habitat (snakes; water/terrestrial)  Behavioral (fireflies; mate signaling)  Temporal (salmon; seasonal mating)  Mechanical (flowers; pollination anatomy)  Gametic (frogs; egg coat receptors)

Reproductive Isolation, II  Postzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adult  Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity)  Reduced hybrid fertility (mule; horse x donkey; cannot backbreed)  Hybrid breakdown (cotton; 2nd generation hybrids are sterile)

Mechanisms for the origin of reproductive isolation  Geographic Barriers  Small populations become separated  Fringe populations become segregated from smaller population  Adaptive radiations  Gene pools become segregated by adaptations to different habitats

Mechanisms for the origin of reproductive isolation  Genetic Barriers  Can be gradual or sudden.  Speciation by diverengence – isolation is secondary consequence between already separated populations.  Separated populations accumulate mutations over time  Barrier produced by prezygotic or postzygotic mechanisms.

Resources to investigate evolution  List of resource material from PBS. 

Evidence for assessing historical population shifts  Paleontology  Phylogenetic systematics  Interplay between dispersal and continental drift  Example: S. America had distinct populations until continental collisions about 3 MYA, when Panamanian uplift connected N. and S. America.

Introduction of Population Biology: Biogeographic Distributions  Cosmopolitan – everywhere  Endemic – restricted to specific regions  Disjunct – separated  Caused by  Dispersal  Vicariance – i. e. continental drift

Biogeography Resources  An excellent online textbook to investigate biomes:  01/textbook/biogeography/outline.html

Biogeographical Heirarchy  Realm – Geographical Distinction  Ecoregion – Function of Climate  Biome – Function of Rainfall  Community – Function of other physical parameters  Ecotone – intermediate plant distribution; characteristics of 2 different communities

Energy Transfer in the Environment  Photosynthesis 6CO 2 +12H 2 O + (Solar Energy) ---> C 6 H 12 O 6 +6O 2 +6H 2 O  Respiration C 6 H 12 O 6 +6O 2 ---> 6CO 2 +6H 2 O+2830 kj  Simplified CO 2 +H 2 O + (Solar Energy) ---> CO 2 + CH 2 O CO 2 +H 2 O + (Solar Energy) ---> CO 2 + CH 2 O

Biomes  Five Principal Biomes – based on unique plant and animal communities.  Forest  Savannah  Grassland  Desert  Tundra

Comparison between a food chain and a food web

Ecology – Trophic Levels  Primary Producers – plants  Consumers – live plants or prey  Decomposers – use energy stored in dead plants or animals

Ecology – Trophic Levels  First Law of Thermodynamics - states that energy cannot be created or destroyed; it can only be changed from one form to another.  Second Law of Thermodynamics - states that whenever energy is transformed, there is a loss energy through the release of heat. This occurs when energy is transferred between trophic levels

Ecology – Trophic Levels

Pond Ecology Resources  Microscopic Pond Life  Virtual Pond  Pond Life Game  Create a Pond Activity  Center for Global Environmental Education

Difference between lake and pond  Lakes are statified by temp and oxygen  Ponds are not for the most part  Can get an estimate by the use of a Secchi Disk.

Other Resources  Find an activity-

Schematic for Virtual Pond