1. Evolution and Biodiversity: Origins, Niches, and Adaptation
APES Chapter 5
Evolution and Biodiversity: Origins, Niches, and Adaptation

2. Origins of Life-2 phases:
Chemical evolution
Biological evolution
Evolution of the organic molecules, biopolymers, and systems of chemical reactions needed to from the first protocells
Lasted approx. 1 billion years
Evolution of single- celled organisms (prokaryotes and then eukaryotes) and then multi-cellular organisms
Took approx billion years.

3. Chemical evolution
billion years ago—cosmic dust cloud condensed to from earth.
4.4 billion years ago—atmosphere was formed— contained NO oxygen.
Energy available—lightening, heat from volcanoes, and UV radiation.
Stanley Miller and Harold Urey provided experimental support the inorganic molecules could combine to form simple organic molecules under the conditions of the primitive Earth.
Organic molecules may have formed membrane – bound protocells.

4. Biological Evolution Protocells evolved into single-celled prokaryotes
billion years ago, evolution of photosynthetic prokaryotes started producing O2
1.2 billion years ago the first eukaryotic cells formed.
million years: first plants on land, then mammals, then man.

5. Origins of Life
Fig. 5-2 p. 96; Refer to Fig. 5-4 p. 98

6. How do we know organisms lived in the past?
Fossils
Relative dating—superposition and index fossils
Absolute dating—radioactive decay rate (half life)

7. Evolution and Adaption
Evolution—the change in a population’s genetic makeup through successive generations. Individuals do not evolve, only populations evolve.

8. Microevolution—describes the small genetic changes that occur in a population.
Macroevolution—describes the long-term, large-scale, evolutionary changes among groups of species.
1. speciation (new species formed from ancestral species)
2. species lost through extinction.

9. How Microevolution Works
There must be a change in the Gene Pool (sum total of all genes possessed by the individuals of a population).
1. mutations—only changes in reproductive cells are passed on to offspring
Random and unpredictable
Most are harmful

10. Natural Selection
Three conditions necessary for evolution by natural selection to occur.
1. natural variability
2. heritable trait
3. differential reproduction-greater chance for one form to reproduce.
Three types of natural selection
1. directional
2. stabilizing
3. diversifying

11. Directional Natural Selection
Number of individuals
Snail coloration
best adapted
to conditions
Average
Coloration of snails
New average
Previous
average
Number of individuals
Coloration of snails
Average shifts
Natural
selection
Proportion of light-colored
snails in population increases
Figure 5-6 (1) Page 102

12. Stabilizing Natural Selection
Coloration of snails
Snails with
extreme
coloration are
eliminated
Number of individuals
Stabilizing Natural Selection
Average remains the same,
but the number of individuals with
intermediate coloration increases
Natural
selection
Light snails
Dark snails
Figure 5-6 (2) Page 102

13. Figure 5-6 (3) Page 102 Diversifying Natural Selection
Number of individuals
with light and dark coloration
increases, and the number with
intermediate coloration decreases
Coloration of snails
Snails with light and dark
colors dominate
Diversifying Natural Selection
Light
coloration
is favored
Dark
Intermediate-colored snails
are selected against
Natural
selection
Figure 5-6 (3) Page 102

14. Coevolution
Interaction between species that results in microevolution in each of their populations.
Ex: flowers and pollinators
predators and prey

15. How Macroevolution Works
Evolution that takes place over an extremely long time involving groups of species.
Speciation—forming a new species
Geographic isolation  reproductive isolation speciation

16. Macroevolution How do species become extinct?
When environmental conditions change, a species may cease to exist if it cannot adapt.
Background extinction—disappearance of species’ at a low gradual rate.
Mass extinction—abrupt rise in extinction rate above the background level catastrophic and worldwide where large numbers of species are eliminated.
We have had five major extinctions with the last being 65 million years ago (at the end of the mesozoic era). A sixth mass extinction is currently happening and caused by humans.

17. Macroevolution
Adaptive radiation—period of recovery, rapid divergent evolution leading to speciation, following mass extinctions.
There are two theories about how rapidly macroevolution occurs:
1. gradualist model of evolution
2. punctuated equilibrium hypothesis—gradual evolution interrupted periodically by rapid speciation.

18. Ecological Niches and Adaptation
Ecological Niche—the species’ way of life or role in an ecosystem. Includes:
Range of tolerance
Type of resources it uses
How it interacts with components of the ecosystem
Fundamental niche—full potential range of physical, chemical, and biological conditions under with an organism could survive.
Realized niche—the actual part of the fundamental niche occupied by the organism.

20. Species can have broad niches (generalists: roaches, flies, coyotes, humans) while other have narrow niches (specialists: spotted owls, giant pandas)
Habitat—the physical location where a species lives.

21. Common Misconceptions Concerning Evolution

22. Evolution Misconceptions
Misconception: “Survival of the Fittest” means survival of the strongest.
Truth: To biologists, Fitness is a measure of reproductive success NOT strength.
Misconception: Evolution involves some grand plan of nature in which organisms are becoming more complex/perfect with time.
Truth: From a scientific standpoint, no plan or goal exists in the evolutionary process.

23. Modern humans (Homo sapiens) appear about 2 seconds before midnight
Plants begin
invading
land
Evolution and expansion of life
First fossil
record of
animals
Plants invade the land
Age of reptiles
Age of mammals
Insects and amphibians invade the land
Modern humans
(Homo sapiens)
appear about
2 seconds
before midnight
Recorded human
history begins
1/4 second
Origin of life
(3.6–3.8 billion
years ago)
noon
midnight