NATURAL SELECTION Flashcards
Who is Charles Darwin?
Darwin proposed the theory of evolution by natural selection in his book “On the Origin of Species” (1859). His work revolutionized scientific understanding of the diversity of life and its adaptation to changing environments.
Alfred Russel Wallace (1823-1913)
Independently formulated the theory of evolution by natural selection. His research in Southeast Asia provided evidence supporting evolutionary theory and spurred Darwin to publish his own ideas.
Darwin and Wallace’ Theory of Natural Selection
Natural selection is the process by which organisms that are better adapted to their environment tend to survive and reproduce more successfully than those that are less adapted.
- It acts on heritable variations within populations, leading to changes in the frequency of traits over successive generations.
Darwin’s Three Postulates
The ability of the population to expand is infinite but the ability of any environment to support the population is always finite.
Organisms with populations vary, and this variation affects the ability of individuals to survive and reproduce.
The Variations are transmitted from parents to offspring
How do his postulates lead to evolutionary change?
Darwin + Galapagos Finches
He went to the islands and wanted to reserach thebeaks of these finches.
The Frank’s Work
1974- PResent: Medium Ground Finch
Variation in beak
Beak depth is heritable variation
Variation is related to resource acquisition
Selection may act against both ends of the range of variation = stasis.
1976-1977: Drought that produced environmental change
Increase in average seed size and hardness
Bird population decreases from 1200 to 400: average beak depth increase 4%
How variation affects survival dynamically (natural selection → of survivors )
Change in environment → “Selections event” → new virus
Variation and reproduction
Next Generation
IS THIS PROGRESS CHANGE TOWARDS PERFECT ORGANISMS
How did the franks illustrated evolutionary change of these finches in the drought?
The observed the rapid shift of beaks as there were earthquakes and dorughts
Macroevolution
The evolution of a new species of creature from ‘parent’ species
Microevolution
changes in the frequencies of characteristics (traits, genes) in a population thru time
Natural Selection
VARIATION IS IMPORTANT W.O IT NO EVOLUTION
NATURAL SELECTION ONLY EDITS VARIATION THAT IS
INHERITED
AFFECTS REPRODUCTIVE SUCCESS
FITNESS = MEASURES AS REPRODUCTIVE SUCCESS (# OF OFFSRPIGN TO REACH REPRODUCTIVE AGE)
. NATURAL SELECTION TARGETS INDIVIDUALS AND THIER PACKAGE OF VARIATION BUT
POPULATIONS (GROUP OF INDIVIDUALS) EVOLE, INDIVIDUALS FO NOT EVOLE.
EVOLUTION CAN BE RAPID.
What were Darwin’s two main problems with his own ideas?
The Blending Problem :Coulndt explains how new variation continually arise and persist within populations
THe Chicuaua Problems: Did not understand the mechanisms of inheritance
How did Gregor Mendel solve the blending problem
SUed the pea plants
What is the principle of segregation?
parents pass on thier traits to their children each parent only gives one version of each traits.
Principle of Independent Assortment?
Traits are passed on to offspring independently of each other. (deck of cards).
