Please enable JavaScript.
Coggle requires JavaScript to display documents.
Speciation & History of Life - Coggle Diagram
Speciation & History of Life
The Origin of Species (Ch.24)
What is the Biological Species Concept?
Species that interbreed and produce fertile offspring
based on reproductive compatibility
focuses on gene flow between populations
example: horse + donkey = mule
explains how scientists define species boundaries
What is Reproductive Isolation
barriers that prevent gene flow between species
Keeps populations genetically seprate
increases genetic divergence over time
allows populations to evolve independently
What are Prezygotic & Postzygotic Barriers?
Prezygotic
barriers before fertilization occurs
prezygotic prevents mating or zygote formation
Example: different mating seasons
postzygotic
barriers after fertilization occurs
postzygotic results in weak or sterile offspring
Exanple: mule sterility
What is Speciation?
Formation of new species from ancestral populations
occurs when gene flow is reduced or stopped
driven by natural selection, mutation, and genetic drift
leads to evolutionary divergence over generations
What is Allopatric vs. Sympatric Speciations?
Allopatric Speciation
Speciation due to geographic isolation
geographic barriers block gene flow
Sympatric Speciation
speciation without geographic separation
polyploidy common in plants
Example: island populations evolving separately
populations adapt to different environments
What are Hybrid Zones & Reinforcement?
hybrid zone is an area where two species meet and mate
hybrids may have lower fitness
reinforcement strengthens reproductive barriers
shows speciation is an ongoing evolutionary process
stability means hybrids continue forming
What Affects the Speed of Speciation?
how quickly new species form over time
strong natural selection accelerates divergence
rapid environmental change can increase speciation
geographic isolation speeds up reproductive isolation
History of Life on Earth (Ch.25)
What were Early Earth Conditions?
Earth was formed about 4.6 billion years ago
volcanic activity and lightning were common
intense UV radiation affected early Earth
conditions allowed origin of life to begin
oceans formed early and supported chemical reactions
What is the Origin of Life on Earth?
abiotic formation of organic molecules before life
organic molecuels became building blocks of cells
simple molecules formed complex organic compounds
First step toward origin of living organisms
What was the Miller-Urey Experiment?
produced amino acids from inorganic molecules
early Earth atmospheric conditions
showed organic molecules can form naturally
key evidence for abiotic synthesis
What were the First Cells (Prokaryotes)?
Earliest life forms about 3.5 billion years ago
prokayotic cells with no nucleus
single-celled and simple structure
ancestors of all modern organisms
anaerobic metabolism (no oxygen required)
The Rise of Oxygen in Earth's Atmosphere
cyanobacteria performed photosynthesis
oxygen released into atmosphere over time
aerobic respiration or mroe energy production
allowed evolution of complex eukaryotic life
What is Endosymbiosis Theory?
eukaryotic cells evolved from engulfed prokaryotes
double membranes are key evidence
binary fission similar to bacteria reproduction
mitochondria originated from aerobic bacteria
chloroplasts orginiated from photosynthetic bacteria
own circular DNA as evidence