1. Evolution and Biodiversity: Origins, Niches, and Adaptations
What is Evolution?
Chapter 5

2. Key Concepts
Origins of life
Evolutionary processes
Ecological niches
Species formation
Species extinction

3. Earth: The Just-Right, Adaptable Planet
During the 3.7 billion years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC.
What other conditions make life on Earth possible?

4. Origins of Life
Evidence suggests that life on earth developed in 2 phases: Chemical Evolution and Biological Evolution
Chemical Evolution
formation of the earth’s crust and atmosphere
evolution of the biological molecules necessary for life
evolution of the systems of chemical reactions needed to produce living cells (protocells)
Fig. 5-2 p. 93

5. Animation on CD H2O CH4 Electrode CO2 N2 NH3 H2 Electrical sparks
Water vapor
Electrode N2
CO2
NH3 H2
Electrical sparks
simulating lighting
provide energy to
synthesize organic
compounds
Condenser
Cold water
Cooled water
containing organic
compounds
H2O
Sample for
chemical
analysis
Animation on CD

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

7. How Do We Know Which Organisms Lived in the Past?
Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.

8. Comparing Anatomy and Embryology
Homologous Structures
Parts that are similar in structure but different in function
Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things
Similar Embryos
Embryos of different organisms are very similar and have similar structures early on
Must have similar proteins at work
Vestigial Structures
Structures that are so reduced in size of function that they are merely traces of similar organs in other species (I.e. tailbone and appendix in humans)
Analogous Structures
Parts that are similar in function but not structure
i.e. Wing of bee, bird, bat

9. Fossils mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items provide physical evidence of organisms Fossil record is INCOMPETE – only found and 1% of the species that are believed to have lived

10. Origins of Life Biological evolution
change in the genetic makeup of a population of a species in successive generations, if continued long enough it can lead to the formation of a new species
How do new genes get into the population: mutations, genetic drift (organisms coming in and out of the population)
Populations – NOT INDIVIDUALS - evolve

11. Evolution and Adaptation
Theory of Evolution – all species descended from earlier, ancestral species. HOMER
Macroevolution - long-term, large-scale evolutionary changes through which
new species are formed from ancestral species and
other species are lost through extinction.

12. Evolution and Adaptation
Microevolution - small genetic changes that occur in a population. Genes mutate, individuals are selected and populations evolve.
Gene pool – set of all genes in the individuals of the population of a species
Mutation – changes in the structure or number of DNA molecules in a cell
Mutations are random, rare, only source of totally new alleles
Exposure to mutagens
Mistakes during replication

13. Evolution and Adaptation
Natural selection
Process in by which individuals of a population acquire genetically based traits that increase their chances of survival and their ability to produce offspring.
Adaptation (n.)
A heritable trait that enables an organism to better survive and reproduce under a given set of environmental conditions
Artificial selection
Humans select one or more desirable genetic traits in the population of a plant or animal.

14. Artificial Selection
The selective breeding of domesticated plants and animals by man.
Question:
What’s the ancestor of the domesticated dog?
Answer: WOLF
This is STELLA!!!!!

15. Natural Selection Directional Selection (peppered moth example)
Conditions necessary for natural selection:
Variability – phenotypic differences in a trait
Heritability – trait must have a genetic basis to evolve
Differential Reproductive Success – phenotypic traits determine individual survival and success
Combination of survival and reproduction is called “fitness”
Survival of the Sneakiest
Directional Selection (peppered moth example)
Stabilizing Selection
Diversifying Selection
Fig. 5-4 p. 96
CD ANIMATION 4

16. Evolution as Genetic Change in Populations
How Natural Selection Works – 3 Types
Stabilizing Selection
Individuals with the average form of a trait have the highest fitness
Represents the optimum for most traits
Results in a similar morphology between most members of the species
Directional Selection
Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait
A shift in one direction
Peppered moth
Disruptive DIVERSIFYING Selection
Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait
A shift in both direction, away from the center
Shell color (dark rocks and light sand)

17. Directional Natural Selection
Snail coloration
best adapted
to conditions
Average
New average
Previous
average
Natural
selection
Number of individuals
Number of individuals
Average shifts
Coloration of snails
Coloration of snails
Proportion of light-colored
snails in population increases

18. Stabilizing Natural Selection
Light snails
eliminated
Dark snails
eliminated
Natural
selection
Snails with
extreme
coloration are
eliminated
Number of individuals
Number of individuals
Coloration of snails
Coloration of snails
Average remains the same,
but the number of individuals with
intermediate coloration increases

19. Diversifying Natural Selection
Intermediate-colored snails
are selected against
Snails with light and dark
colors dominate
Natural
selection
Light
coloration
is favored
Dark
coloration
is favored
Number of individuals
Number of individuals
Coloration of snails
Coloration of snails
Number of individuals
with light and dark coloration
increases, and the number with
intermediate coloration decreases