1. Evolution and Biodiversity
Miller Chapter 5

2. Earth: The Just Right Planet
Temperature
Distance from Sun
Geothermal energy from core
Temperature fluctuated only 10-20oC over 3.7 billion years despite 30-40% increase in solar output
Water exists in 3 phases
Right size (=gravitational mass to keep atmosphere)
Resilient and adaptive
orbit around sun: leads to seasonal patterns

3. Origins of Life on Earth 4.7-4.8 Billion Year History
Evidence from chemical analysis and measurements of radioactive elements in primitive rocks and fossils.
Life developed over two main phases:
Chemical evolution (took about 1 billion years)
Organic molecules, proteins, polymers, and chemical reactions to form first “protocells”
Biological evolution (3.7 billion years)
From single celled prokaryotic bacteria to eukaryotic creatures to eukaryotic multicellular organisms (diversification of species)

4. Summary of Evolution of Life
Formation
of the
earth’s
early
crust and
atmosphere
Small
organic
molecules
form in
the seas
Large
(biopolymers)
First
protocells
Single-cell
prokaryotes
eukaryotes
Variety of
multicellular
organisms
form, first
in the seas
and later
on land
Chemical Evolution
(1 billion years)
Biological Evolution
(3.7 billion years)

5. Biological Evolution
Fossils present but rare
Evolution and expansion of life
Fossils become abundant
Plants invade the land
Age of reptiles
Age of mammals
Insects and amphibians invade the land
Modern humans (Homo sapiens) appear about 2 seconds before midnight
Recorded human history begins 1/4 second before midnight
Origin of life (3.6–3.8 billion years ago)

6. Fossil Record
Most of what we know of the history of life on earth comes from fossils
Give us physical evidence of organisms
Show us internal structure
Uneven and incomplete record of species
We have fossils for 1% of species believed to have lived on earth
Some organisms left no fossils, others decomposed, others have yet to be found.
Other info from ancient rocks, ice core, DNA

7. Evolution Microevolution Macroevolution
The change in a POPULATION’S genetic makeup (gene pool) over time (successive generations)
Those with the best phenotype and genotype survive to reproduce and pass on traits
All species descended from earlier ancestor species
Microevolution
Small genetic changes in a population such as the spread of a mutation or the change in the frequency of a single allele due to selection (changes to gene pool)
Not possible without genetic variability in a pop…
Macroevolution
Long term large scale evolutionary changes through which new species are formed and others are lost through extinction

8. Microevolution four processes drive microevolution:
gene flow: the movement of genes between populations;
genetic drift: change in genetic composition that results by chance, especially in small populations.
mutation: random changes in the structure of DNA molecules that serve as the ultimate source of genetic variation;
natural selection: the process by which some individuals of a population have genetically based characteristics that cause them to survive & produce more offspring than other individuals;

9. Natural Selection
When individuals in a population have certain genetic traits that enhance their ability to survive and pass on these advantageous traits to their offspring.
Adaptation- heritable trait that enables the organisms to better survive under environmental conditions.
When faced with changing environmental conditions a species will either:
1) adapt through natural selection
2) migrate to areas with more favorable conditions
3) become extinct!

10. Darwinian Natural Selection
Three conditions necessary for evolution by natural selection to occur:
Natural variability for a trait in a population
Trait must be heritable (has a genetic basis so that it can be passed onto offspring)
Trait must lead to differential reproduction
Must allow some members of the population to leave more offspring than other members of the population w/o trait)
A heritable trait that enables organisms to survive is called an adaptation

11. Steps of Evolution Genetic variation is added to genotype by mutation
Mutations lead to changes in the phenotype
Phenotype is acted upon by nat’l selection
Individuals more suited to environment produce more offspring (contribute more to total gene pool of population)
Population’s gene pool changes over time
Speciation may occur if geographic and reproductive isolating mechanisms exist…

12. Take Home #1
When faced with a change in environmental condition, a population of a species can:
Adapt via natural selection
Migrate (if possible) to an area with more favorable conditions (Mars & Atlantis?)
Become extinct
Natural selection can only act on inherited alleles already present in the population—do not think that the environment creates favorable heritable characteristics!

14. Three types of Natural Selection
Directional
Allele frequencies shift to favor individuals at one extreme of the normal range
Only one side of the distribution reproduce
Population looks different over time
Peppered moths and genetic resistance to pesticides among insects and antibiotics in bacteria
Stabilizing
Favors individuals with an average genetic makeup
Only the middle reproduce
Population looks more similar over time (elim. extremes)
Diversifying
Environmental conditions favor individuals at both ends of the genetic spectrum
Population split into two groups

15. 1. Directional Selection
Directional selection favors individuals with traits that are at one end of a distribution (such as the peppered moth example). "It pays to be different."

16. Directional Change in the Range of Variation
Directional Selection
Shift in allele frequency in a consistent direction
Phenotypic Variation in a population of butterflies

17. The Case of the Peppered Moths
Industrial revolution
Pollution darkened tree trunks
Camouflage of moths increases survival from predators
Directional selection -shift away from light-gray towards dark-gray moths

18. 2. Stabilizing Selection
Stabilizing selection eliminates individuals at both in of the spectrum of variation; the average remains the same. "It pays to be average."

19. Selection Against or in Favor of Extreme Phenotypes
Stabilizing Selection
Intermediate forms of a trait are favored
Alleles that specify extreme forms are eliminated from a population

20. 3. Diversifying Selection
Diversifying selection eliminates average individuals, but favors individuals at either extreme of the spectrum of variation. "It doesn't pay to be normal."

21. Selection Against or in Favor of Extreme Phenotypes
Disruptive Selection
Both forms at extreme ends are favored
Intermediate forms are eliminated
Bill size in African finches

22. Coevolution Interactions between species can cause microevolution
Changes in the gene pool of one species can cause changes in the gene pool of the other
Adaptation follows adaptation between interacting populations of different populations
Can also be symbiotic coevolution
Angiosperms and insects (pollinators)
Corals and zooxanthellae
Rhizobium bacteria and legume root nodules

23. Coevolution examples:
flowering plants & their pollinators; flowers attract pollinators & provide "reward" for food in the form of nectar or pollen; pollinators perform "service" of moving pollen between flowers;
plants with defenses against herbivores (thorns, camouflage, toxins) & the herbivores’ ability to deal with plants’ defenses.

24. the species’ occupation and its
Niche is
the species’ occupation and its
Habitat
location of species
(its address)

25. Niche
A species’ functional role in its ecosystem; includes anything affecting species survival and reproduction
Range of tolerance for various physical and chemical conditions
Types of resources used
Interactions with living and nonliving components of ecosystems
Role played in flow of energy and matter cycling

26. Niche
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

27. Niche Overlap separation Number of individuals Generalist species
Region of
niche overlap
Generalist species
with a broad niche
with a narrow niche
Niche
breadth
separation
Number of individuals
Resource use

28. 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
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.
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
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)

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.

30. r and k strategists
Depending upon the characteristics of the organism, organisms will follow a biotic potential or carrying capacity type reproductive strategy
The r-strategists
High biotic potential – reproduce very fast
Are adapted to live in a variable climate
Produce many small, quickly maturing offspring = early reproductive maturity
“Opportunistic” organisms
The K-strategists
Adaptations allow them to maintain population values around the carrying capacity
They live long lives
Reproduce late
Produce few, large, offspring

31. Speciation Two species arise from one Requires Reproductive isolation
Geographic: Physically separated
Temporal: Mate at different times
Behavioral: Bird calls / mating rituals
Anatomical: Picture a mouse and an elephant hooking up
Genetic Inviability: Mules

32. Speciation example Reproductive Isolation

33. The Case of the Road-Killed Snails
Study of neighboring populations of snails
Genetic variation is greater between populations living on opposite sides of the street
Color -
3 alleles of a gene

34. Speciation
Geographic isolation can lead to reproductive isolation, divergence, and speciation.

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

36. Adaptive Radiation
Adaptive radiation involves splitting of a lineage to form many species with different ecological niches. The adaptive radiation of mammals began about 65 million years ago.

37. Evolutionary Divergence
Each species has a beak specialized to take advantage of certain types of food resource.

39. Extinction 99.9% of all species that ever existed are now extinct.
Background extinction- species disappear at a low rate
Mass extinction and mass depletion
Background vs. Mass Extinction
Low rate vs % of total
Five great mass extinctions in which numerous new species (including mammals) evolved to fill new or vacated niches in changed environments
10 million years or more for adaptive radiations to rebuild biological diversity following a mass extinction

40. Extinction in the context of Evolution
If the environment changes rapidly and
The species living in these environments do not already possess genes which enable survival in the face of such change and
Random mutations do not accumulate quickly enough then
All members of the unlucky species may die

41. Human Activities are Decreasing Biodiversity
Richest areas of biodiversity- tropical forests, coral reefs, and wetlands

42. Biodiversity Speciation – Extinction=Biodiversity
Humans major force in the premature extinction of species. Extinction rate increased by times the natural background rate.
As we grow in population over next 50 years, we are expected to take over more of the earth’s surface and productivity. This may cause the premature extinction of up to a QUARTER of the earth’s current species and constitute a SIXTH mass extinction
Genetic engineering won’t solve this problem
Only takes existing genes and moves them around
Know why this is so important and what we are losing as it disappears….

43. 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.

44. 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

45. Date of the Extinction Event Marine vertebrates and invertebrates
Mass Extinctions
Date of the Extinction Event
Percent Species Lost
Species Affected
65 mya
(million
years ago) 85
Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected.
213 mya 44
Marine vertebrates and invertebrates
248 mya
75-95
380 mya 70
Marine invertebrates
450 mya 50

46. 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.

47. Continental Drift
Continental drift, slow movement of continents, has played a major role in both speciation and extinction.

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

49. 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.

50. 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.