1. Warm-Up Questions How old is the Earth?
How long ago did life originate on Earth?
What did the first life-forms look like?
How long ago did dinosaurs go extinct?
How long ago did human beings appear on Earth?

2. Warm-Up Questions How did life emerge on Earth?
How do we know what organisms lived in the past?
What is the theory of evolution?
What is natural selection?
What is artificial selection?
What does “survival of the fittest” mean?

3. Evolution and Biodiversity: Origins, Niches, and Adaptations
What is Evolution?
Chapter 5

4. Key Concepts
Origins of life
Evolutionary processes
Ecological niches
Species formation
Species extinction

5. 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?

6. 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)

7. H2O CH4 Electrode N2 CO2 NH3 H2 Condenser Cold water H2O
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

8. Origins of Life http://www.youtube.com/watch?v=iahBQolXQH8

9. Origin of life (3.6–3.8 billion years ago)
Modern humans
(Homo sapiens)
appear about
2 seconds
before midnight
Recorded human
history begins
¼ 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

10. History of the Earth Calendar
First living cells - April 1st, 6pm
Algae & Marine Invertebrates - November 26th, 4:24am
Arthropods, Mollusks, first fish - December 1st, 6:36am
Many fish, trilobites, vascular plants - December 5th, 7:42am
Age of fishes, first amphibians, first insects - December 7th, 4:24am
Mosses, many amphibians, first reptiles - December 13th, 6pm
First mammals and dinosaurs - December 16th, 10:14pm
Age of Dinosaurs, first birds - December 19th, 1:03am
Flowering plants, mass extinction - December 23rd, 5:54am
Birds and mammals flourish - December 28th, 1:09am
Hominids, ice ages, giant mammals - December 31st, 9:09pm

11. 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

12. 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

13. Comparing Anatomy and Embryology
Analogous Structures
Parts that are similar in function but not structure
Ex: wings of bee, bird, bat

15. Comparing Anatomy and Embryology
Similar Embryos
Embryos of different (but related) organisms are very similar and have similar structures early on
Must have similar proteins at work

16. Comparing Anatomy and Embryology
Vestigial Structures
Structures that are so reduced in size of function that they are merely traces of similar organs in other species
Ex: tailbone and appendix in humans

17. 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

18. Fossils
"It isn't easy to become a fossil… Only about one bone in a billion, it is thought, becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today – that's about 310 million people with 206 bones each – will only be about 50 bones, one-quarter of a complete skeleton. That's not to say, of course, that any of these bones will ever actually be found. Bearing in mind that they can be buried anywhere within an area of slightly over 9.3 million square kilometers, little of which will ever be turned over, much less examined, it would be something of a miracle if they ever were” ~ Bill Bryson

19. 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

20. 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

21. 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

22. 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

23. Artificial Selection
The selective breeding of domesticated plants and animals by man.
Question:
What’s the ancestor of the domesticated dog?
Answer: WOLF

24. Natural Selection 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”
Fig. 5-4 p. 96
CD ANIMATION 4

25. 3 Types of Natural Selection
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
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)

26. Warm-Up
What is the difference between stabilizing, directional, and diversifying natural selection?

27. 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

28. 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

29. 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

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

31. 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 (number of offspring) versus some other species

32. Common Myths about Evolution through Natural Selection
Misconception #1: Survival of the fittest means 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”

34. 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
Plant defense mechanisms

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

36. 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
Parts of a species’ fundamental niche that are actually used

37. 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
Ex: 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
Ex: tiger salamander, spotted owls, pandas

38. 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

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

40. 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

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

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

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

45. 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

46. Extinction Background extinction Mass extinction
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

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

48. 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

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