BIOLOGY 1500 OUTLINE FOR CHAPTER 4
Evolution and Biodiversity
Evolution definitions to know:
1. Biological evolution
2. The theory of evolution
3. Microevolution
4. Macroevolution
5. Natural selection
6. Gene pool
7. Mutation
8. Adaptation
Evidence of Evolution (there are five)
1) fossils: skeletons of organisms trapped in bedrocks and sediments and date back to
as much as millions of years
2) Homologuous body structures: similar bone arrangement in the skeletons of
animals is considered to be an evidence of evolution from a common ancestor.
3) Embryology: the early embryo of many animals is highly similar
4) Genetic evidence:
a. Cytochrome C: a protein found in many organisms and is considered an
evidence of common ancestors given its abundance in different organisms
b. Human DNA: the research confirms the “Out of Africa” hypothesis that all
modern humans stem from a single group of Homo sapiens who emigrated
from Africa 2,000 generations ago and spread throughout Eurasia over
thousands of years
5) Biogeography: it studies the distribution of plants and animals and the processes
that influence their distribution including evolution and natural selection. Only
geologic change and evolution can explain the distribution of many species such as
the distribution of camel-like animals.
Steps of the Evolution by Natural Selection
Excess individuals produced
Struggle for existence
Mortality of excess individuals
Variation that affects survival and reproduction
Variation is heritable
Favorable traits will be passed down and unfavorable traits will be eliminated
Result, more individuals will have favorable traits over time.
Ecological Niches
Niche: refers to the “job” or “role” of an organism in its habitat. It includes all of the
variation in environmental factors within which an organism can survive and
reproduce.
An example is the Placentals versus the Marsupials occupying similar niches at
geographically distinct locations.
Two types of Niches
Fundamental niche: is the range of all possible environments in which an
organism could live in absence of competition, predation, or parasitism
Realized niche: consists of the environment(s) in which an organism is
actually found in nature.
Habitat
Refers to the location and kind(s) of communities in which an organism lives; its
home or address
Species
A species is a group of organisms that resemble each other in terms of appearance,
lifestyle, behavior, chemistry, and genetics (a variation of the morphological species
concept). Also: is a set of individuals that can mate and produce fertile offspring.
Generalists: live in a very wide range of habitats and have very broad fundamental
niches
Specialists: live in a few habitats (or maybe just one) and have very narrow niches.
Both (generalists and specialists) can succeed in a stable environment
Generalists are more successful in an unstable or variable environment
Misconceptions about Evolution:
1. If a trait is not available to counteract a threat, then organism cannot
adapt, it dies
2. Fittest does not equal strongest
3. There is no plan to move to perfection; all organisms are bundles of
compromises.
Speciation
The common mechanism of speciation involves reproductive and geographic
isolation and evolution in different environments. Happens due to a barrier: first
geographic (such as river, street, wind, tectonic plates, volcano…etc) then
reproductive isolation.
Extinction and Biodiversity
Extinction
- extinction is the fate of all species
- there is a constant low extinction rate called the background extinction rate.
Every year one in million species goes extinct.
- Speciation minus extinction equals biodiversity
- The largest cause of the growing rate of species extinctions and ecosystem
disruptions is the loss, fragmentation, and degradation of terrestrial and aquatic
habitats.
- Mass extinction:
o Involves episodes in which more than 25% (up to 95%) of species are
wiped out.
o Extinction rates greatly above background.
o Is important, because it allows new groups of organisms to take over
many niches in the long run. However, in the short run it greatly lowers
biodiversity and results in ecosystem collapse.
Biodiversity
variety of different species (species diversity), genetic variability among
individuals within each species (genetic diversity), variety of ecosystems
(ecological diversity), and functions such as energy flow and matter cycling
needed for the survival of species and biological communities (functional
diversity).
Artificial Selection
- Process by which humans select one or more desirable genetic traits in the
population of a plant or animal species then use selective breeding to produce
populations containing many individuals with the desired traits.
- Promotes those traits in other organisms that are beneficial to humans.
- Artificial selection can increase diversity in pets and other non-food animals.
- It can also increase uniformity (decrease diversity) and productivity in crops.
Biotechnology (genetic engineering)
- Genetic engineering transfers traits from one organism to another.
- Creates pesticides resistance, such as Round-Up ready corn by Monsanto.
- Uses bacteria to produce human insulin.
- Creates novel combinations not found in nature.
- Unintended consequences: BT corn pollen can poison more than just corn pests.
Kills monarch butterfly.
- Divided reaction to GM foods: Increasing adoption in some countries, banning in
others
Commonalities
Both artificial selection and genetic engineering can decrease diversity in
some organisms (such as potato) and increase it in others (such as dogs),
while making novel combinations not found in nature.