1. Evolution and Biodiversity

2. Overview Questions
How do scientists account for the development of life on earth?
What is biological evolution by natural selection, and how can it account for the current diversity of organisms on the earth?
How can geologic processes, climate change and catastrophes affect biological evolution?
What is an ecological niche, and how does it help a population adapt to changing the environmental conditions?

3. Overview Questions (cont’d)
How do extinction of species and formation of new species affect biodiversity?
What is the future of evolution, and what role should humans play in this future?
How did we become such a powerful species in a short time?

4. Rest assured, you are not alone!

5. 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

6. In the Beginning…according to Science
Chemical Evolution- (hypothesis) the first organic (life forming) molecules formed from inorganic molecules and energy; formed protocells
Lightening; Heat (geothermal); Radiation (UV-sun)
Produced by Stanley Miller and Harold Urey
Biological Evolution-the change in a populations’ genetic make-up through successive generations (takes time; not on an individual basis)
Evidence from fossils (comparative anatomy) and DNA

7. 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

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

9. Recorded human history begins about 1/4 second before midnight
Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight
Recorded human history begins about 1/4 second before midnight
Age of mammals
Age of reptiles
Insects and amphibians invade the land
Origin of life ( billion years ago)
Figure 4.3
Natural capital: greatly simplified overview of the biological evolution by natural selection of life on the earth, which was preceded by about 1 billion years of chemical evolution. Microorganisms (mostly bacteria) that lived in water dominated the early span of biological evolution on the earth, between about 3.7 billion and 1 billion years ago. Plants and animals evolved first in the seas. Fossil and recent DNA evidence suggests that plants began invading the land some 780 million years ago, and animals began living on land about 370 million years ago. Humans arrived on the scene only a very short time ago—equivalent to less than an eye blink of the earth’s roughly 3.7-billion-year history of biological evolution.
First fossil record of animals
Plants begin invading land
Evolution and expansion of life
Fig. 4-3, p. 84

10. 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

11. 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.

12. The Theory Evolution
Evolution Theory- the idea that all species descended from earlier, ancestral species
Explains HOW life has changed and why life is so diverse
Gene Pool- a populations’ genetic make-up (all the genes found in the individuals in a population)
Microevolution- small genetic changes that occur in a population
Macroevolution- long-term, large scale changes; cause 2 outcomes:
New species are formed from ancestral species
Other species are lost through extinction

13. How Evolution Occurs
Mutation- a random change in the structure (alleles) or number of DNA molecules in a cell; 99% fatal;
Mutagens-radiation (gama, x-ray, UV) or natural or man-made chemicals
Abnormalities- mistakes made during the copy process when cells divide or during reproduction
Natural Selection- the process through which some individuals exhibit traits that increase their chances of survival and ability to produce offspring; 3 required conditions
Variability of trait in species
Must be heritable, able to be passed from one generation to another
Differential Reproduction- increase the number of offspring or survivability of offspring of an individual

14. Adaptation
Natural Selections Causes (1) alleles or sets of alleles that are beneficial to become more common in successive generations and (2) other less beneficial alleles to become less common
Adaptation- the improved ability of an organism to survive and reproduce; a specific trait that increases these chances is called and adaptive trait; often caused by the environment and do one of the following:
Species adapt through natural selection
Migrate to another area
Become extinct

15. 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.

16. Directional Selection
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
Directional Selection

17. Stabilizing 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
Stabilizing Selection

18. Disruptive Selection 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
Disruptive Selection

19. Natural Selection
Fig. 5-5 p. 101
Coevolution- the hypothesis that the population of two interacting species (over a long-term) can cause changes in the gene pool that affect changes in the gene pool of the other species

20. 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.

21. 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

22. 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.

23. 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.

24. 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.

25. 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

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

27. 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.

28. 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.

29. 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

30. 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

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

32. Avocet sweeps bill through mud and surface water in
search of small crustaceans,
insects, and seeds
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Herring gull is a
tireless scavenger
Brown pelican dives for fish,
which it locates from the air
Dowitcher probes deeply
into mud in search of
snails, marine worms,
and small crustaceans
Black skimmer
seizes small fish
at water surface
Louisiana heron wades into
water to seize small fish
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Figure 4.8
Natural capital: specialized feeding niches of various bird species in a coastal wetland. Such resource partitioning reduces competition and allows sharing of limited resources.
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Flamingo
feeds on
minute
organisms
in mud
Scaup and other
diving ducks feed on mollusks, crustaceans,and aquatic vegetation
Knot (a sandpiper)
picks up worms and
small crustaceans left
by receding tide
(Birds not drawn to scale)
Fig. 4-8, pp

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

34. 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.

35. Speciation, Extinction, and Biodiversity
Geographic isolation
Reproductive isolation

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

37. 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

38. Extinction Background extinction- due to
environmental changes; occurs slowly
Mass extinction- catastrophic and or
widespread;
Adaptive radiation- occurs just after a
mass extinction when many niches are
available in the changed environment

39. 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

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

41. 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

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

43. 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

44. 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

45. 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
Transfer to soil
Figure 4.14
Genetic engineering: steps in genetically modifying a plant.
Transgenic plants
with new traits
Fig. 4-14, p. 95

46. Grow Genetically Engineered Plant
Transgenic cell
from Phase 2
Phase 3
Grow Genetically Engineered Plant
Cell division of
transgenic cells
Culture cells
to form plantlets
Transfer to soil
Transgenic plants
with new traits
Stepped Art
Fig. 4-14, p. 95

47. How Would You Vote?
Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available?
a. No. Human cloning will lead to widespread human rights abuses and further overpopulation.
b. Yes. People would benefit with longer and healthier lives.

48. 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.

49. 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?

50. 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).