1. Evolution and Biodiversity
LT1: Chapter 4
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. protocells form in the seas Single-cell prokaryotes
Chemical Evolution
(1 billion years)
Biological Evolution
(3.7 billion years)
Formation
of the
earth’s
early
crust and
atmosphere
Large
organic molecules
(biopolymers)
form in
the seas
Variety of
multicellular
organisms
form, first
in the seas
and later
on land
First
protocells form in the seas
Single-cell prokaryotes
form in
the seas
Small organic
molecules
form in
the seas
Single-cell
eukaryotes
form in
the seas
Figure 4.2
Natural capital: summary of the earth’s hypothesized chemical and biological evolution by natural selection. This drawing is not to scale. Note that the time span for biological evolution by natural selection is almost four times longer than that for chemical evolution.
Fig. 4-2, p. 84

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

6. Animation: Evolutionary Tree of Life
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ANIMATION

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.
Figure 4-4

8. 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.

9. 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.

10. Animation: Stabilizing Selection
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ANIMATION

11. Animation: Disruptive Selection
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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. 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.

14. 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.

15. 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.

16. 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

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

18. 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.

19. 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.

20. 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

21. Specialized Feeding Niches
Resource partitioning reduces competition and allows sharing of limited resources.
Figure 4-8

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

23. 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.

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

25. 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

26. 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

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

28. GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION
We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding.
We have used genetic engineering to transfer genes from one species to another.
Figure 4-15

29. Genetic Engineering: Genetically Modified Organisms (GMO)
GMOs use recombinant DNA
genes or portions of genes from different organisms.
Figure 4-14

30. Identify and remove portion of DNA with
Phase 1
Make Modified Gene
E. coli
Genetically
modified
plasmid
Insert modified
plasmid into E. coli
Cell
Extract
Plasmid
Extract DNA
Plasmid
Gene of
interest
DNA
Identify and remove portion of DNA with
desired trait
Remove plasmid
from DNA of E. coli
Insert extracted
(step 2) into plasmid
(step 3)
Identify and extract gene with desired trait
Grow in tissue
culture to
make copies
Figure 4.14
Genetic engineering: steps in genetically modifying a plant.
Fig. 4-14, p. 95

31. Transfer plasmid copies to a carrier agrobacterium
Phase 2
Make Transgenic Cell
A. tumefaciens
(agrobacterium)
Foreign DNA
E. Coli
Host DNA
Plant cell
Nucleus
Transfer plasmid copies to a carrier agrobacterium
Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell
Figure 4.14
Genetic engineering: steps in genetically modifying a plant.
Transfer plasmid to surface of microscopic metal particle
Use gene gun to inject
DNA into plant cell
Fig. 4-14, p. 95

32. Grow Genetically Engineered Plant
Phase 3
Grow Genetically Engineered Plant
Transgenic cell
from Phase 2
Cell division of
transgenic cells
Culture cells
to form plantlets
Figure 4.14
Genetic engineering: steps in genetically modifying a plant.
Transfer to soil
Transgenic plants
with new traits
Fig. 4-14, p. 95

33. THE FUTURE OF EVOLUTION
Biologists are learning to rebuild organisms from their cell components and to clone organisms.
Cloning has lead to high miscarriage rates, rapid aging, organ defects.
Genetic engineering can help improve human condition, but results are not always predictable.
Do not know where the new gene will be located in the DNA molecule’s structure and how that will affect the organism.

34. Controversy Over Genetic Engineering
There are a number of privacy, ethical, legal and environmental issues.
Should genetic engineering and development be regulated?
What are the long-term environmental consequences?

35. Case Study: How Did We Become Such a Powerful Species so Quickly?
We lack:
strength, speed, agility.
weapons (claws, fangs), protection (shell).
poor hearing and vision.
We have thrived as a species because of our:
opposable thumbs, ability to walk upright, complex brains (problem solving).