How Populations Evolve

How Populations Evolve
Charles Darwin and Alfred Wallace are the fathers of the theory
of evolution.
Darwin's main ideas centered on ------------------------, how species
change over time, and the ----------------------------------------------. "
Origin of Species" which mainly proposes ------------------------- as
a mechanism for evolution (survival of the fittest)
Jean Baptiste Lamarck:( before Darwin) suggested that life evolves
but the mechanism he suggested was mistaken. He proposed the -----------------------------------------------------------------------------Evolution:
Origins of Earth: earth is approx. 4.6 billion years old(BYBP)
- oldest fossil of prokaryotic cells 3.5BYBP
- oldest fossils of eukaryotic cells 2.2BYBP
- humans ~ 1.8MYBP
 First cells were --------------------------------, eating organic
molecules in oceans
 first autotrophs were -------------------------, blue - green algae
 cells became more specialized, had organelles for certain
 all living organisms have same characteristics, composed of
cells, take energy, reproduce, evolve
 all living things are related, common ancestor, became
diverse because of the different environments and ways of
Evidence of Evolution:
1. Fossils: remains or trace of -------------------------------,
footprints, imprints, bones, teeth, shells, skeletons,
usually ------------------------------------. We have a
missing record of things, like studying a book with
missing pages. Fossils give us ideas of older versus
younger organisms. We have a fossil record that is ----------------------------------------------------------------------.
Sedimentations occur in layers called ----------------,
where the -------------------------- are found in the bottom
strata and the ------------------------------ are contained in
the upper strata. Get a view of different species that
might have become extinct over time. Ex: The "Ice
Man" was preserved in ice 5000 yrs. ago.
2. Biogeographical evidence:
3. Comparative anatomical evidence: comparison of body
structures in different species.
4. Embryological evidence: Related organisms have
similar stages during embryonic development.
5. Molecular evidence:
Population Evolution
gene pool:
Microevolution is the change in a population's gene pool over time.
The frequencies of the alleles encoding the various traits can
change over time.
The gene pool of a non-evolving population remains --------------------------------------------------------------------Hardy - Weinberg Law of genetic equilibrium: allele
frequencies in a population will remain stable over time IF there
p = % dominant alleles in a population
p2 + 2pq + q2 = 1
q = % of recessive alleles in a population
p2 = % homozygous dominant individuals
2pq = % of heterozygous individuals
q2 = % homozygous recessive individuals
In real life, these conditions are never met and thus allele
frequencies change creating evolution.
Four factors cause evolution:
1. Mutations:
2. Genetic drift:
- founder effect
- bottleneck effect:
3. Gene flow:
4. Natural selection:
. There are many types of outcomes for natural selection:
- Stabilizing selection:
- Directional selection:
- Diversifying selection
Evolution leads to Speciation:
Species: a group of populations that share a gene pool, the
members can breed and produce fertile offspring.
Best Example: Charles Darwin in Galapagos islands: 13 different
species of finches descended from mainland finches. Birds look
similar to each other but have very different beaks depending on
where they live and what they eat.