Essential knowledge 1.C.1:_ Speciation and extinction have occurred throughout the Earth’s history. https://www.youtube.com/watch?v=yJLRl2G41nQ&lis t=PLFCE4D99C4124A27A&index=9

Speciation and Extinction

Speciation rates can vary, especially when adaptive radiation occurs when new habitats become available. Adaptive Radiation - a process in which organisms diversify rapidly into a multitude of new forms Often occurs when a change in the environment makes new resources available and opens environmental niches

Species extinction rates are rapid at times of ecological stress. 5 Major extinctions

6th mass extinction? Human impact on ecosystems and species extinction rates

Speciation and Extinction - Bozeman https://www.youtube.com/watch?v=yJLRl2 G41nQ&list=PLFCE4D99C4124A27A&in dex=9

Essential knowledge 1.C.2: Speciation may occur when two populations become reproductively isolated from each other.

Macroevolution: the origin of new taxonomic groups Speciation: the origin of new species

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)

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)

Modes of speciation (based on how gene flow is interrupted) Allopatric: populations segregated by a geographical barrier; can result in adaptive radiation (island species) Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

Punctuated equilibria Tempo of speciation: gradual vs. divergence in rapid bursts; Niles Eldredge and Stephen Jay Gould (1972); helped explain the non- gradual appearance of species in the fossil record

Essential knowledge 1.C.3: Populations of organisms continue to evolve.

Two significant concepts: 1. Scientific evidence supports the idea that evolution has occurred in all species. All life on Earth is descended from a last universal ancestor that lived approximately 3.8 billion years ago. Repeated speciation and the divergence of life can be inferred from shared sets of biochemical and morphological traits, or by shared DNA sequences

Two significant concepts: 2. Scientific evidence supports the idea that evolution continues to occur. Examples: • Chemical resistance (mutations for resistance to antibiotics, pesticides, herbicides or chemotherapy drugs occur in the absence of the chemical) • Emergent diseases • Observed directional phenotypic change in a population (Grants’ observations of Darwin’s finches in the Galapagos) • A eukaryotic example that describes evolution of a structure or process such as heart chambers, limbs, the brain and the immune system

Speciation – Bozeman https://www.youtub e.com/watch?v=rlf Nvoyijmo&list=PLF CE4D99C4124A27 A