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Evolution & Natural Selection - Coggle Diagram
Evolution & Natural Selection
Evidence of Evolution
Theory of Evolution
Organisms change over time as a result of heritable traits passed down to generations
microevolution
Species change in small ways, such as size or color, over generations
macroevolution
Many accumulated changes over time create new species
How scientists provide evidence of evolution
Comparative anatomy to determine common ancestor
Study of the similarities and differences in the structures of different species
Homologous structures
Structures are similar in related organisms due to common ancestor
Similar structure
different function
common ancestor
Analogous structures
Similar structures in unrelated organisms
differing structure
similar function
no common ancestor
vestigial structure
structure is present in a species but no longer useful
DNA to determine common ancestor
Molecular Clock
Determines how closely related two species are based on the number of differences between their DNA sequences.
Biogeography
How and why organisms live where they do.
How organisms in one location are related to those in another location.
Adaptive radiation
Species evolve based on differing environmental conditions
Natural Selection
Organisms that are best suited to their environment produce more offspring than other organisms. Over time, beneficial traits become more common in the population.
Fitness refers to an organism's ability to survive and reproduce.
Types of natural selection
divergent evolution
two or more species with different characteristics evolve from a common ancestor.
Convergent evolution
organisms that live in similar habitats develop similar structures from different ancestors.
Conditions for natural selection to occur
More offspring are born than can survive
variation of organisms within a species
variations are inherited
For variations within a species to drive natural selection, those variations must be genetically based.
selective pressures
Factors that impact survival
predation
disease
competition for space
abiotic conditions
competition for food
select for individuals that are more genetically fit
outcompete other species
find food
win territories
avoid predation
carry resistance to disease
thrive in environmental abiotic conditiions
Diversity of Killer Whales
The transition from subspecies to species takes hundreds or thousands of generations.
Scientists discovered 2 subspecies of killer whales
Residential
feeds on herring
remain in area year-round
Hunting strategies: large pods and vocalize a lot
heavy wear on teeth
Migratory
migrate to follow prey
feeds on marine mammals
Hunting strategies: travel in small groups and hunt in silence
teeth remain strong and in tact
Charles Darwin
Observations of biodiversity on Galapagos Islands
Led to Theory of Evolution
Mechanisms of evolution
Speciation
Over time, separate populations of a species may develop enough separate adaptations that they no longer breed with one another.
Adaptive radiation
One ancestor gives rise to several different species
Can occur due to variations in habitat conditions
Genetic Drift
Random event changes the genetic makeup of a population
bottleneck effect
Natural disasters often kill a large portion of a population. The survivors may not have all of the genes that were originally present in the population.
founder effect
Small groups have different genes from the original population due to chance.
allopatric speciation
Natural selection acts on each new population separately. The two populations cannot interbreed because of the barrier separating them.
Reproductive isolation
Geography or other factors prevent two populations from breeding with each other.
Keeps genes from the original population from mixing back into the new population. This often causes the gene pool to change very quickly.
Subspecies
two populations can still interbreed, but they have enough differences that scientists can easily tell them apart.
Coevolution
Two species interact so often that each affects how the other evolves.