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 Cara

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”
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

20. Evolution Primers Isn't Evolution Just a Theory???
How Does Evolution Really Work?
How Do We Know Evolution Happens?

21. Limits on Adaptation through Natural Selection
A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.
Humans have a relatively slow generation time (decades) and output (# of young) versus some other species.

22. Common Myths about Evolution through Natural Selection
Evolution through natural selection is about the most descendants.
Misconception 1: survival of the fittest does not mean survival of the strongest – it is referring to REPRODUCTIVE SUCCESS
Misconception 2: Evolution involves some grand plan of nature in which species become progressively more perfect
Organisms do not develop certain traits because they need them.
There is no such thing as genetic perfection.

24. Evolution and Adaptation
Co-Evolution
Populations of two different species interacting over a long period of time
Changes in the gene pool of one species can lead to changes the gene pool of another species
Predator-Prey Relationships (salamander and snake – the coffee pot incident)
Plant defense mechanisms (mistletoe plant)

25. Ecological Niches and Adaptation
Occupation
Ecological niche
Total way of life or functional role of a species in an ecosystem.
Habitat
Physical location of a species
Address

26. Ecological Niches and Adaptation
Fundamental niche
Full potential range of the physical, chemical, and biological factors a species can use if there were no direct competition from other species.
Realized niche
Part of a species fundamental niche that are actually used.

27. Broad and Narrow Niches
Generalist species
Species with a broad ecological niche.
Live in many different places.
Eat a variety of food.
Tolerate a wide range of environmental conditions.
(flies, mice, deer, catfish, humans)
Specialist species
Species with a narrow ecological niche.
Live only in one type of habitat
Use only a few types of food
Tolerate only a narrow range of climatic and other environmental conditions.
(tiger salamander, red-cockaded woodpecker, spotted owls, pandas)

28. Generalist and Specialist Species: Broad and Narrow Niches
Generalist species tolerate a wide range of conditions.
Specialist species can only tolerate a narrow range of conditions.

29. Is it better to be a Generalist or a Specialist?
Answer: It depends.

30. Speciation, Extinction, and Biodiversity
Speciation - formation of two species from one species because of divergent natural selection
Geographic isolation – groups of the same species become physically separated

31. Geographic Isolation
…can lead to reproductive isolation, divergence of gene pools and speciation.

32. Speciation, Extinction, and Biodiversity
Reproductive Isolation – isolated populations become so genetically different they cannot . . .
Interbreed, or
produce live, fertile offspring

33. Extinction: Lights Out
Extinction occurs when the population cannot adapt to changing environmental conditions.
The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate.

34. Extinction: Lights Out
99.9 % of all species that ever existed are now extinct

35. Species and families experiencing mass extinction
Bar width represents relative
number of living species
Millions of
years ago
Era
Period
Extinction
Current extinction crisis caused
by human activities. Many species
are expected to become extinct
within the next 50–100 years.
Quaternary
Today
Cenozoic
Tertiary
Extinction 65
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Cretaceous
Mesozoic
Jurassic
Extinction
Triassic: 35% of animal families, including many reptiles and marine mollusks.
180
Triassic
Extinction
Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.
250
Permian
Carboniferous
Extinction
345
Figure 4.12
Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities.
Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.
Devonian
Paleozoic
Silurian
Ordovician
Extinction
500
Ordovician: 50% of animal families, including many trilobites.
Cambrian

36. Extinction Background extinction Mass extinction Adaptive radiation
Normal extinction of various species as a result of changes in local environmental conditions
Mass extinction
extinction resulting from catastrophic, wide-spread event in which large groups of existing species are wiped out
Adaptive radiation
Process in which numerous new species evolve to fill vacant and new ecological niches in changed environments

37. Period of Recovery Following Extinction
Adaptive radiation -
Process in which numerous new species evolve to fill vacant and new ecological niches in changed environments

38. How do speciation and extinction affect biodiversity?
Speciation – Extinction = Biodiversity
Extinctions and depletions temporarily reduce biodiversity YET create evolutionary opportunities for surviving species to undergo adaptive radiations to fill unoccupied and new biological niches

39. Effects of Humans on Biodiversity
The scientific consensus is that human activities are decreasing the earth’s biodiversity.