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Chapters 24 + 25 - Coggle Diagram
Chapters 24 + 25
Chapter 25
Key events in Life's HIstory
Timeline
3.5b years ago 1st prokaryotes
1.8 bya = first eukaryotes
1.3bya = 1st multicellular eukaryotes
535-525 mya = cambrian explosion
500mya = colonization of land
Key events = colonization of land, formation of unicellular/multicellular organisms
The Rise and Fall of Organism Groups
plate tectonics = continental plates move gradually overtime, alters geography
history of evolution punctuated by 5 mass extinctions
radically altered life's history
adaptive radiations = periods where many new species form and fill roles in their communities
The Fossil Record
Fossil record shows rise and fall of species/organisms
Radiometric dating = method of estimating age of fossils using isotopes
Fossil record shows gradual modification of organisms
Major changes in body form
developmental genes effect differences between species
can influence change as organism matures
evolution of new forms can be caused by changes in genes or gene regulation
Conditions on Early Earth
Experiments simulated early earth conditions
Organic molecules synthesized
Can form into protocells
Protocells = membrane-bound droplets that share cell properties
1st genetic material may have been RNA
Evolution
Evolution = not goal-oriented
evolution can occur gradually based on development of beneficial modifications
can be caused by natural selection or species selection
results from interactions between organisms + their environments
Chapter 24
The Biological Species Concept
A species = group of populations that can interbreed successfully with each other but not with members of other species
Requirements = fertile, viable offspring
Occurs via reproductive isolation
Reproductive isolation = barriers to species members producing viable, fertile offspring
Prezygotic barriers
Occur before fertilization
Postzygotic barriers
Occur after fertilization
Types of Speciation
Speciation = process where species splits into 2+ other species
Types
Allopatric
Gene flow reduced when species members geographically separated
Sympatric
New species originates in same geographic area
Example = polyploidy (condition where organism has extra chromosome sets)
Hybrid Zones
Hybrid zones = regions where members of species meet and breed
Outcomes
fusion
species "fuse" to become one big species
Stability
hybrid offpsring continue to be produced overtime
reinforcement
Natural selection strengthens prezygotic barriers
Speed of Speciation
Divergence required for speciation
Speciation can happen quickly or slowly