EEMB Week 2

______: process by which one species splits into two species

speciation

Speciation is a bridge between ________ and _________

microevolution and macroevolution

• speciation bridge is mechanism why which new species originate from existing ones

_______ species concept: defines species as set of organism adapted to a particular set of resources (niche) in environment

ecological

_______ species concept: classifying organisms into species based on morphology

morphological

• linnaean system of classification uses MSC

______ species: group of actually or potentially interbreeding natural populations that are reproductively isolated

biological

• biological species concept: uses breeding behavior as basis for demarcating species

biological species parameters

• Species are:

• populations of organisms that interbreed with each other

• or could possibly breed, under natural conditions

• and reproductively isolated from other groups

Reproductive isolation

existence of biological factors or barriers that impede members of two species from interbreeding and producing viable, fertile offspring

• prezygotic

• postzygotic

  

• there’s 3 questions on exam about prezygotic and 1 about postzygotic

• know examples, the text won’t just be definitions, it’ll have stories

Prezygotic isolating mechanisms

• lead to reproductive isolation by preventing formation of hybrid zygotes

  • habitat isolation

  • temporal isolation

  • behavioral isolation

  • mechanical isolation

  • gametic isolation

Habitat isolation

gene flow restricted because populations come to occupy different habitats within same area

Temporal isolation

• individuals from two populations mate at different times

  • species not reproductive or active at same time

    

Behavioral isolation

• populations develop differences in courtship rituals or response to the, therefore are unable to mate successfully

  • different behaviors don’t attract mate of other species

Mechanical isolation

• morphological or anatomical differences preclude successful mating

  • species physically incompatible

  • “lock and key” model

    

Gametic isolation

• biochemical or cellular changes create incompatibility between gametes, so sperm can’t fertilize egg

  

_____________ mechanisms: occur after gametes fuse. They reduce survival or reproductive success of hybrids, preventing gene flow between species

postzygotic isolating mechanisms

• there are three major types:

  • hybrid inviability

  • hybrid sterility

  • hybrid breakdown

____________: genes of different parent species may interact in ways that impair hybrid’s development or survival in its environment

reduced hybrid viability

_____________: even if hybrid survives and thrives, they may be sterile

reduced hybrid fertility

_________: some first-generation hybrids are viable and fertile, but when they mate with another or with either parent species, offspring of next generation are weak/and or sterile

hybrid breakdown

Limitations of biological species concept

Difficulties in determining when one species has changed into another

it may not be possible to identify an exact point at which change occurred

Types of speciation

_______ speciation: population first separated by geographical barriers

_______ speciation: populations reproductively isolated even though share same geographical area

1. allopatric

   1. evidence: snapping shrimp divided by isthmus of Panama

   2. more common in nature

2. sympatric

   1. can occur if gene flow reduced by polyploidy habitat differentiation, and sexual selection

Hybrid zones

• region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

• patterns within hybrid zones: form narrow bands of land between two habitats

• hybrid zones and environment change: changing environmental conditions can alter where habitats of interbreeding species meet

• there might be one question on the exam about hybrid zones

Hybrid zones over time

______: reinforcing reproductive barriers (natural selection should strengthen prezygotic barriers to reproduction)

______: two hybrid species fuse into single species

______: hybrids continue to be produced, sometimes because hybrids survive or reproduce better than members of either parent species (at least in certain habitats or years)

1. reinforcement

2. fusion

3. stability

Speciation can be slow or rapid

• patterns in fossil record

  • ________: change as they branch and then change very little thereafter

  • ________: slow and steady

1. punctuated equilibrium

2. gradualism

should know this for the exam

From speciation to macroevolution

• speciation might begin with small differences

• BUT… as this occurs repeatedly, differences accumulate and become more pronounced eventually leading to formation of new groups of organisms that differ greatly from their ancestors

  • we can see this very clearly in fossil record

  • on to macroevolution

Macroevolution is evolution ______ species level

above

How do we document life’s history?

• Fossil Record

  • ________: forms from sediment, which is made up of pieces of rock, minerals, and organic matter

    • can preserve remains or remnants of ancient animals and plants

    • form layers, so older layers further down than newer layers

  • ______: hardened resin

  • ____________: some fossils (like petrified tree trunk) form as minerals and seep into and replace organic matter

  • _____, ____, _____: can preserve body of larger organisms (rare- but it happens!)

  • ________: fossil record of biological activity by lifeforms but not preserved remains of organism itself

1. sedimentary rock

2. amber

3. mineralized organic matter

4. frozen soil, ice, acid bog

5. trace fossils

The Fossil Record

• how rocks and fossils are dated:

  • _________: when “parent” isotope decays to “daughter isotope” at characteristic rat

  • _________: time required for 50% of parent isotope to decay

  • Fossils frame _______: standard time scale that divides Earth’s history into 4 eons and additional subdivisions

  • _________: layered rocks that form when certain prokaryotes bind thin films of sediment together

    • earliest evidence of life (3.5 bya)

1. radiometric dating

2. half-life

3. geologic record

4. stromatolites

Fossils can provide details about origins of ______ organisms

1. new

ex. origin of mammals

Rise and fall of groups of organisms

• Life on earth filled with rise and fall of groups of organisms

• _________ originated, flourished, and then declined as oxygen content of atmosphere rose

  • first tetrapod emerged from sea, giving rise to multiple groups of organisms

    • ______ dominated terrestrial environment for 100 million years until other tetrapods replaced them as dominant vertebrates

1. anaerobic prokaryotes

2. amphibians

• rise and fall of organisms is related to speciation and extinction rates of its member species

  • occurs when more new species produced than are lost to extinction

Plate tectonics is a scientific theory that explains how major landforms created as result of Earth’s subterranean movements.

• Plate tectonics explains “HOW” behind continental drift theory

  • main features of plate tectonics:

    • Earth’s surface covered by series of crustal plates

    • ocean floors constantly moving; spreading in center and sinking at edges and being regenerated

    • convection currents beneath plates assist movement

    • heat from mantle drives these currents

Speciation and Extinction Rates

• consequences of _______:

  • alters habitat in which organisms live

  • climate change resulting from continents changing locations

  • promotes allopatric speciation on very large scale

    

continental drift

Background and Mass Extinctions have different causes

• mass extinctions due to extraordinary and sudden changes to environment

• background extinctions occur mostly as result of natural selection

  

6th mass extinction?

• consequences of mass extinctions?

  • reduce ecological communities to almost nothing

  • altering ecological communities by changing types of organisms residing there

• Are we in midst of 6th mass extinction?

  • how will we decide?

  • what evidence do we have?

  • over last 500 million years, extinction rates have tended to increase when global temperatures were high

Adaptive radiation

• process in which organisms diversify rapidly from ancestral species into new forms, particularly when change in environment makes new resources available, alters biotic interactions, or opens new niches

_______ radiations:

• mammals undergo AR after extinction of terrestrial dinosaurs 66 mya

  • with disappearance of dinosaurs, mammals expanded in diversity and size, filling ecological roles once occupied by terrestrial dinosaurs

______ radiations: Hawaiian islands

1. worldwide adaptive radiations

2. Regional adaptive radiations

Genetic effects

• major changes in body form can result from changes in sequences and regulation of developmental genes

  • evo-devo: research at interface of evolutionary biology and developmental biology

  • examines how slight genetic differences can produce major morphological differences between species

Genetic mechanisms of change

• effects of developmental genes

  • _________: evolutionary change in rate or timing of developmental events

    • ex. humans/chimps: genetic mutations in humans slowed growth of jaw relative to other parts of skull

      

• changes in rate and timing

  • ________: condition where sexually mature stage of species may retain body features that were juvenile structures in ancestral species

    • usually occurs if development of reproductive organs accelerate compared to that of other organs

• changes in spatial pattern:

  • _________: genes that control pattern of body formation during early embryonic development of organisms

1. heterochrony

2. paedomorphosis

3. homeotic genes

Evolution is not goal oriented!

• evolutionary trends: does not imply that there is some intrinsic drive toward particular phenotype