1. Evolution and Biodiversity
Chapter 4a
Evolution and Biodiversity

2. Core Case Study 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.
Figure 4-1

3. ORIGINS OF LIFE
1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change.
Figure 4-2

4. Biological Evolution
This has led to the variety of species we find on the earth today.
Figure 4-2

5. 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.
Figure 4-4

6. EVOLUTION, NATURAL SELECTION, AND ADAPTATION
Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.
genetic variability
Mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.

7. Animation: Stabilizing Selection
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ANIMATION

8. Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits
Three conditions are necessary for biological evolution:
Genetic variability, traits must be heritable, trait must lead to differential reproduction.
An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.

9. Animation: Disruptive Selection
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ANIMATION

10. Animation: Moth Populations
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ANIMATION

11. Animation: Adaptive Trait
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ANIMATION

12. Coevolution: A Biological Arms Race
Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other.
This often happens between predators and prey species.

13. Hybridization and Gene Swapping: other Ways to Exchange Genes
New species can arise through hybridization.
Occurs when individuals to two distinct species crossbreed to produce an fertile offspring.
Some species (mostly microorganisms) can exchange genes without sexual reproduction.
Horizontal gene transfer

14. 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.

15. Common Myths about Evolution through Natural Selection
Evolution through natural selection is about the most descendants.
Organisms do not develop certain traits because they need them.
There is no such thing as genetic perfection.

16. GEOLOGIC PROCESSES, CLIMATE CHANGE, CATASTROPHES, AND EVOLUTION
The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones.
The locations of continents and oceanic basins influence climate.
The movement of continents have allowed species to move.

17. 225 million years ago 225 million years ago 135 million years ago
Figure 4.5
Geological processes and biological evolution. Over millions of years the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species as land areas split apart and promote the rise of new species when once isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s huge plates separated and eventually resulted in today’s locations of the continents (bottom right).
65 million years ago
Present
Fig. 4-5, p. 88

18. Climate Change and Natural Selection
Changes in climate throughout the earth’s history have shifted where plants and animals can live.
Figure 4-6

19. Catastrophes and Natural Selection
Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

20. ECOLOGICAL NICHES AND ADAPTATION
Each species in an ecosystem has a specific role or way of life.
Fundamental niche: the full potential range of physical, chemical, and biological conditions and resources a species could theoretically use.
Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

21. 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.
Figure 4-7

22. SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors
350 million years old
3,500 different species
Ultimate generalist
Can eat almost anything.
Can live and breed almost anywhere.
Can withstand massive radiation.
Figure 4-A

23. Evolutionary Divergence
Each species has a beak specialized to take advantage of certain types of food resource.
Figure 4-9

24. SPECIATION, EXTINCTION, AND BIODIVERSITY
Speciation: A new species can arise when member of a population become isolated for a long period of time.
Genetic makeup changes, preventing them from producing fertile offspring with the original population if reunited.

25. Geographic Isolation
…can lead to reproductive isolation, divergence of gene pools and speciation.
Figure 4-10

26. 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.
Figure 4-11

27. 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
Fig. 4-12, p. 93

28. Effects of Humans on Biodiversity
The scientific consensus is that human activities are decreasing the earth’s biodiversity.
Figure 4-13