Evolution lecture 5 Flashcards
What is evolution?
the process by which the inherited characteristics of populations change over generations, leading to the eventual formation of new species
- is ongoing
- is the principle that all life shares a common ancestor
What are the names of the two scientists who discovered and described the mechanism for evolution?
Charles Darwin and Alfred Russel Wallace
What did Darwin do?
- Was a naturalist
- Visited South America, Australia, Africa
What did Wallace do?
- was a naturalist who studied insects
- collected insects in 1848-1852
-1854 -1862 collected insects in Malay archipelago
What were Darwin’s finches
- Darwin observed that each island had its own finch species
- the finches were very similar to one another and also a finch species on the mainland in South America
- species had unique beak shapes
- very small differences in beak size/ shape between the most similar
- Darwin thought that the island species might all be modified from one original mainland species
- Beaks adapted differently on each island in order to better allow the finches to acquire different food sources
What are the 3 Natural Selection?
is the inevitable result of three principles that operate in nature
1) characteristics of organisms are inherited ( i.e from parents to offspring)
2) more offspring are produced than are able to survive ( i.e. not all can survive and reproduce due to limited resources)
3)offspring have different characteristics are inherited
What is adaptation?
A heritable trait that aids the survival and reproduction of an organism in its present environment
What is divergent evolution? Provide example
-The process by which different organisms having common ancestors develop different traits or characteristics to adapt to the changing environmental conditions and needs
- accumulation of differences between groups that can lead to new species formation
Example: vertebrate limb
- structure shows common origins
- blind cave fish
What is convergent evolution? Provide example.
-the process whereby distantly related organisms independently evolve similar traits to adapt to similar necessities.
when similar structures arise through evolution independently in different species
- even though features in a species may look the same as those in another species, they do not share any recent common ancestry
- any similarity due to adaptations in response to similar environmental pressures
Examples: wings used in flight
- evolved independently in insects, birds and bats
- wings look similar and are used for similar purpose
- but not a close relationship between insects, birds, and bats
- vision in human and octopus
- very similar eyes, but evolved independently not a close evolutionary relationship
- white color of artic fox and ptarmigan bird
- animals living in the arctic have temporary white coverings during winter to blend with the snow and ice
- both adapted white color to avoid predation
- no common ancestor who was white
What is analogous structure? Provide example.
Structures that are similar in function and appearance BUT do not share a common ancestor
Example: wings of bats and insects
What is Homologous structure? Provide example.
Structures that share similarities, despite differences resulting from evolutionary divergence
- did not evolve independently, but have common ancestor who shares that structure
- similarities in anatomy between species often shows their descent from a common ancestor which had a similar physical form
Example:
Bones in the appendages of a human, dog, bird, and whale share same overall construction and common ancestor
- wings of hummingbird and ostrich
both are birds and descended from a common ancestor with wings
- wings did not evolve independently in each bird lineage
What is vestigial structure? Provide example
A structure in an organism that has no apparent function at all, and appear to be a residual part from a past ancestor
Example: wings on flightless birds, traces of pelvic bones in whales and snakes
- appendix in humans
What is changing allele frequencies in a population? Provide example.
- Allele frequencies change due to natural selection
- If an allele confers an advantageous phenotype (i.e. individual survives longer and reproduces more), that allele will be inherited by those offspring and in greater frequency in the next generation
- Since allele frequencies always add up to 100%, when frequency of one allele increases, others decrease
- Highly beneficial alleles may become fixed
- this means every individual of the population may carry the allele after a few generations
Example:
- E.g. wing colour of peppered moths
- gene for wing color shows mendelian autosomal inheritance
* Before industrial revolution in UK, most moths
were light (dd)
* Blended better against the bark of trees and
could better avoid predation
After industrial evolution, soot from coal turned
tree trunks black
* Moths with dark wings (DD or Dd genotype) were
now better at blending with trunks and avoiding
predation
* Colour of moth population shifted from light to
dark
* Now the air is cleaner, and moth population is
mostly white again
What is mutation?
random changes to genetic material
What is migration into or out of population? Provide example
new individuals/loss of individuals causes changes in ratio of organisms with specific alleles in a population
-gene flow is the flow of alleles in and out of a population resulting from the migration of individuals or gametes
Example: allele for brown color in beetles is introduced into green beetle population
