Interactions
Environments & Organisms
From Pages 86 - 93

1.  Natural Selection: processes that bring about change in species

• Speciation:  production of a new species from previously existing species.
• One population becomes 2 isolated populations.
• Each population has some different genetic variants.
• Mutations for new genetic variants build up over time as the two populations face different environmental challenges.
• If the two populations are separated for a long enough time period ---> two different species.

2.  Extinction

• The loss of an entire species
• Common feature of the evolution of organisms
• The environment does not remain constant
• If a species lacks the genetic resources to answer the changes in the environment, it goes extinct.
• = the fate of most species is extinction

3.  Figure 5.14.  Scene from the last ice age:  most of these mammals are extinct.

4.  Natural selection is constantly at work shaping organisms to fit a changing environment.

• How do humans fit into extinctions of other species?
• Speed the rate of extinction through
• Habitat destruction
• land conversion - from forest to agriculture to urban landscapes
• Fragmentation through road building
• Introduction of exotic invasive species - “weedy” species of plants and animals that have no natural controls on growth
• Rare species are the most threatened with extinction

5.  Coevolution:  2 or more species can reciprocally influence the evolutionary direction of the others.

6.  Organism Interactions

• Predation
• Grazing: animals eating plants
• Carnivory: animals eating animals
• Competition: use of the same resource
• Intraspecific (within a species)
• Interspecific (between different species)
• Symbiosis: long lasting relationship between 2 species

7.  Predation: predator and prey

8.  Competition:  2 strive to obtain the same limited resource.

9.  Competitive Exclusion: 2 species can not occupy the same niche.

• Competition causes organisms to spend energy.
• If 2 species completely overlap for every need (food, nesting sites, nest materials, dust bath sites ….) then one will win, one will lose.
• How to avoid competitive conflict: niche specialization or partitioning.

10.  Niche specialization:  warblers  partition the resource (tree) in their search for insects.

11.  Symbiosis

• Parasitism: one organism (parasite) lives on or in another (host)
• Commensalism: one organism benefits, the other is not affected.
• Mutualism: both species benefit

12.  Parasitism: ectoparasite

13.  Parasitism: endoparasite

14.  Parasitism: plant on plant

15.  Commensalism: shark with remora

16.  Mutualism: root nodules with N2 fixing bacteria