1. Evolution and Biodiversity
Evolution is change over a given period of time.
*All Things Evolve

2. Essential Questions
Be able to describe how the earth is “just right” for life
What is evolution? How has evolution lead to the current diversity of organisms?
What is an ecological niche? How does it relate to adaptation to changing environmental conditions?
How do extinction of species and formation of new species affect biodiversity?

3. Earth: The “Goldilocks” 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
Each species here today represents a long chain of evolution and each plays a role in its respective ecosystem

4. 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)

5. Definitions Evolution – is a gradual change over time
Fossil – is any trace or remains of an organism that has been preserved by natural processes.

6. Evidence of Evolution
Fossils – the study of fossils provides the strongest evidence for evolution of organisms
Living Organisms – the study of anatomical similarities, embryological development, and biochemistry.
Genetics

7. 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)

8. Fossil Record
Most of what we know of the history of life on earth comes from fossils (SJ Gould)
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
The whale as an example Other evidence here

9. Transitional Fossils
- is the fossilized remains of a life form that illustrates an evolutionary transition

10. Anatomical Similarities
Comparative anatomy (Homologous Structures) – study of structural similarities and differences among living things.
Embryological Similarities – comparison of the embryological development of different species.
Biochemical similarities – comparison of biochemical life processes between different organisms. Ex production of proteins from amino acids.

11. Comparative anatomy

12. Embryological Similarities

13. Analogous Structures
Two structures in biology are said to be analogous if they perform the same or similar function by a similar mechanism but evolved separately. Ex. The wing of a Bird and Bat

14. Vestigial structures
are anatomical structures of organisms in a species, which have lost much or all of their original function through evolution.
They are typically in a degenerate, atrophied, or rudimentary condition.

15. Fossils and Evolution

16. Charles Darwin Known as the Father of Evolution
Wrote book On the Origin of Species
Sailed the world on a ship called the Beagle

17. 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)

18. Darwin

19. 6 Main Points Of Darwin's Theory
Over production - organisms produce far more offspring than are needed to replace the parents. Most do not live to reproduce age keep the population about the same.
Competition – Since resources are limited competition occurs. This limits the number of offspring that live to reproductive age.
Variation - Offspring are not 'carbon-copies' of their parents; there is widespread heritable variation
Adaptations – Because of variations some individuals will be better adapted to survive and reproduce
Natural Selection – the environment selects the organism with optimal traits to be the parents of the next generation. Thus passing on those favorable traits to their offspring
Speciation – Over many generations natural selection favors certain adaptations which accumulate in a species causing the formation of a new species (speciation)

20. Rate of Evolution or Speciation
Gradualism – evolution occurs slowly and continuously over a long period of time. Made up of the gradual accumulations of small variations
Punctuated Equilibrium – a species remains the same over extended periods of time then it is interrupted, or punctuated by a short period of rapid evolution

21. 4 major mechanisms that drive evolution:
Natural Selection
Mutation
Gene Flow
Genetic Drift

22. Natural Selection
Over time natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness (ability to survive and reproduce) in its environment.
The environment causes struggles for existence and survival of the fittest. (Natural Selection)

23. Sources of Variation
Mutations – changes in DNA sequence. These may or may not affect an organisms fitness.
Gene shuffling – is the random shuffling of genes caused by sexual reproduction.
Migration – Migration into or out of the population. Taking genes away or bringing in new genes to a population

24. Variation Continued
Genetic Drift - In small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population.

25. Natural Selection on Polygenic Traits
Natural Selection can affect the distribution of phenotypes in a population in any of three ways: directional, disruptive and stabilizing.

26. Steps of Evolution by Natural Selection
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…
Natural Selection in action ...
A demonstration...

27. Types of Natural Selection
Directional Selection – occurs when natural selection favors a single allele and therefore allele frequency continuously shifts in one direction.
Stabilizing Selection – is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value
Disruptive Selection - is a type of evolution that simultaneously favors individuals at both extremes of the distribution. (aka Diversifying)

29. 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
EX: Birth Weight and Clutch Size

30. Stabilizing Selection
Coloration of snails
Light snails
eliminated
Dark snails
Number of individuals
Snails with
extreme
coloration are
Average remains the same
Number of individuals with
intermediate coloration increases
Eliminates Fringe Individuals
Natural
selection

31. 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

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

33. Directional Selection
Pesticide Resistance
Pest resurgence
Antibiotic Resistance
Grant’s Finch Beak Data
With directional selection, allele frequencies tend to shift in response to directional changes in the environment

34. Gene Pools
A gene pool is the combined genetic information of all the members of a particular population.
A gene pool typically has two or more alleles for a given trait.
Homozygous lethal traits can be carried by heterozygous individuals and thus remain in a gene pool.
Relative Frequency is the number of times an allele occurs in a gene pool compared with the number of times other alleles occur.

35. Hardy-Weinberg
Genetic equilibrium takes place when allele frequencies remain constant.
In order for genetic equilibrium to take place, five factors must remain true.
1. random mating
2. Large Population
3. No movement in or out of the population
4. No Mutations
5. No Natural Selection

36. Take Home #1
When faced with a change in environmental condition, a population of a species can get MAD:
MIGRATE to a more favorable location
ALREADY be adapted
DIE
Natural selection can only act on inherited alleles already present in the population—do not think that the environment creates favorable heritable characteristics!
Soooo….how do new alleles arise??????

37. MUTATIONS, MY FRIENDS! Changes in the structure of the DNA
Adds genetic diversity to the population
May or may not be adaptive
Depends on the environment!

38. Sooooo….What’s Evolution?
The change in a POPULATION’S genetic makeup (gene pool) over time (successive generations)
Those with selective advantages (i.e., adaptations), survive and reproduce
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…
Processes cause Microevolution
Mutation (random changes in DNA—ultimate source of new alleles)
Exposure to mutagens or random mistakes in copying
Random/unpredictable relatively rare
Macroevolution
Long term, large scale evolutionary changes through which new species are formed and others are lost through extinction

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

40. Peppered Moths of England
The evolution of the peppered moth over the last two hundred years has been studied in detail.
Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light-colored trees and lichens which they rested upon.

41. Peppered Moth Continued
However, due to widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees which peppered moths rested on became blackened by soot, causing most of the light-colored moths, or typica, to die off due to predation.
At the same time, the dark-colored, or melanic, moths, carbonaria, flourished because of their ability to hide on the darkened trees
Now that coal burning plants need to be cleaner there is less pollution and the dark moths are beginning to lose the battle of natural selection

42. Directional selection caused a shift away from light-gray towards dark-gray moths
Fig. 18.5, p. 287

43. Types of Speciation
Reproductive Isolation occurs when members of two populations cannot interbreed. At that point, they have different gene pools.
Behavioral Isolation – Two populations capable of interbreeding but have differences in courtship rituals or other types of behavior.
Geographic Isolation – Populations are separated by geographic barriers such as rivers, mountains, or bodies of water.
Temporal Isolation – Species reproduce at different times of the year.

44. Speciation Northern Arctic Fox Spreads northward and
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Gray Fox
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Spreads
northward
and
southward
separates
Southern
population
Northern
Early fox

45. TAKE HOME #2
Macroevolution is the cumulative result of a series of microevolutionary events
Typically seen in fossil record
Nobody around to see the small, gene pool changes over time.

46. Galapagos Finches
Speciation in the Galapagos Finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition.

47. Survival
Variation within a species help insure that some will survive major changes in the environment.
Major diversity of species also insure that some of the species will survive major environmental changes.

48. Convergent Evolution
is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

49. Coevolution is the mutual evolutionary influence between two species.
                                        
Bumblebees and the flowers they pollinate have co-evolved so that both have become dependent on each other for survival.

50. Evolution in front of your eyes
ANTIBOITIC RESISTANT BACTERIA
We made antibiotics
This killed most of the bacteria
But the bacteria that survived had a variation
That variation was passed to their offspring and now some antibiotics no longer work
We created an environment which selected against most bacteria and through natural selection that have evolved to survive

51. Pesticide resistance
The chemical arsenal we have developed in an attempt to rid our homes of rodents and our crops of insects is losing its power.
We have simply caused pest populations to evolve, unintentionally applying artificial selection in the form of pesticides.
Individuals with a higher tolerance for our poisons survive and breed, and soon resistant individuals outnumber the ones we can control.

52. Factors which Influence the rate of Evolution
Selection pressures: Competition for resources in the environment
Generation Time: The time required for a given population to double in size
Number of offspring: How many offspring they can produce

53. Adaptations
An inherited trait that improves chances of survival and reproduction
Types of Adaptations
Structural Adaptations: Changes in the body structure of an organism
Adaptations for Protection:
Camouflage: Blending with the environment
Warning Coloration: Bright Colors = Danger
Mimicry: Resemble other organism

54. Species with the most favorable adaptations
Are most likely to survive, reproduce and pass their adaptations onto their offspring.
Therefore they are the best adapted organisms (They are the fittest)

55. Species and families experiencing mass extinction years ago Period Era
Ordovician: 50% of animal families,
Devonian: 30% of animal families,
Permian: 90% of animal families, including
over 95% of marine species; many trees,
amphibians, most bryozoans and
brachiopods, all trilobites.
Triassic: 35% of animal families, including
many reptiles and marine mollusks.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Current extinction crisis caused
by human activities.
Species and families experiencing
mass extinction
Bar width represents relative
number of living species
Extinction
Millions of
years ago
Period
Era
Paleozoic
Mesozoic
Cenozoic
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Today 65
180
250
345
500

56. Extinction Local, ecological and true extinction
The ultimate fate of all species just as death is for all individual organisms
99.9% of all the species that have ever existed are now extinct
To a very close approximation, all species are extinct
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
Extinctions open up new opportunities for speciation and adaptive radiation..BUT you can have too much of a good thing!

57. Factors Affecting Extinction Rates
Natural Extinctions
Climate change
Cataclysmic event (volcano, earthquake)
Human Activities
Habitat Loss/Fragmentation
Introduction of exotic/invasive species
Pollution
Commercial harvesting
Accidental killing (tuna nets)
Harassing
Pet Trade
Urbanization
Damming/Flooding
Agricultural conversion

58. Extinction in the Context of EvolutionIf
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