CHAPTER 5 EVOLUTION, ORIGIONS, NICHES & ADAPTATION
A. All life is made of cells
1. Cells have genes (DNA)
2.
Cells are Eukaryotic – DNA in a nucleus or Prokaryotic – no distinct nucleus – still
has DNA example Bacteria
B. Naming Species
1. Use binomial nomenclature
2. Kingdom – Phylum – Classes – Order – Family – Genus – Species
3. Use Latin – organisms have two names
Genus species
Ursus
Homo sapiens,
americanus
Emergence of life on earth
A. Evolution – slow process of change
1. The evolution of life is linked to the chemical and physical evolution of the earth
2. Takes place in two steps – chemical evolution and biological evolution
a. Chemical Evolution
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cloud of cosmic dust condensed into planet earth
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Turned molten due to meteorites and heat of radioactive decaying elements
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Volcanic eruptions released water vapors and other gases into primitive atmosphere
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CO2, N2, H20, CH4, NH3, H2S, HCl
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Energy from lightning, and intense UV caused these simple molecules to form more complex
organic molecules (Oparin’s hypothesis) - Abiogensis
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Carbohydrates – Lipids – Proteins – RNA – Protocells
b. Biological Evolution protocells – Theory of Endosymbotic evolution Lynn Margulis
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Anaerobic Prokaryotes in seas – Photosynthetic cyanobacteria – Oxygen builds up to provide
ozone – protection from UV light (3.6 to 3.8 bya)
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Eukaryotes in the sea
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Invertebrates in the sea
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Vertebrates in the sea
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Green plants move on the land (780 mya)
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Amphbians and insects move to land (370mya)
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Age of reptiles (200-65 Mya)
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Age of mammals (60 mya)
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Humans
c. Evidence
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fossils
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samples of DNA – unfortunately in fossils, DNA replaced by minerals (no such thing as
Jurassic park!)
3. Microevolution – small genetic changes that occur within a population of a species
a. Current theory with most evidence is Natural Selection developed by Darwin
from studying the diversity of the Galapagos islands
b. Three conditions are necessary for the evolution of a population by natural
selection:
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genetic variation (There must be natural variability for a trait a population)
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those best adapted survive and reproduce (differential reproduction – The trait must enable
individuals to leave more offspring than other members of the population)
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pass traits on to offspring - (heritable)
Natural selection causes any allele or set of alleles that result in a beneficial trait to
become more common in succeeding generations
A heritable trait that enables organisms to better survive and reproduce is called an adaptation.
c. Limitations to adaptation
1. Adaptations are limited to traits already in the gene pool
2. Organisms must do many things – adaptations are compromises ex. seal
3. All Organisms in a population may die before enough organisms with the trait can reproduce
Most members would need to die or become sterile before trait is widespread in population
Example of microevolution by Natural Selection:
Camouflage of the peppered moth in England :
d. Mutations add to genetic variation
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changes to DNA – due to mutagen
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totally random
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only source of new genetic material
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very rare
e. Three types of Natural Selection
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Directional natural selection Changing environmental conditions cause allele frequencies
to shift so individuals with traits at one END of the normal range become common. (DRAW)
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changing environmental conditions push majority of individuals of become like the extremes.
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Most common when members of a species move to a new habitat.
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ex. Pays to be different
Peppered moths in pollution areas
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Stabilizing natural selection (Selects for the average or normal conditions)
The environment changes very little – members are well adapted
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eliminates extremes of individuals
ex. Pays to be average
peppered moths before pollutions
- Diversifying natural selection or Disruptive natural selection
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environmental conditions favor individuals at both extremes
reduces the individuals with normal traits
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usually changes with food disruption
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ex. Bird beaks, insect vs seed eaters
f.
Coevolution
1.
when two organisms evolve together selects for traits that favor both populations
2. hawks and mice (predator – prey relationship) , Bird-oxpecker and the black rhino
ECOLOGICAL NICHES: The role an organism plays in nature.
Involves:
a) its range of tolerance
b) types and amount of resources it uses
c) how it uses these resources
d) how it interacts with the other biotic and abiotic components of the ecosystem
e) the role it plays in the energy flow and matter recycling
Why is examining a species niche important?
1) prevents species from premature extinction
2) assess the environmental changes we make in ecosystems- (clearing a forest)
Realized vs Fundamental Niche:
Fundamental Niche – The full potential range of physical, chemical, and biological conditions and
resources a species could theoretically use if there were no direct competition from other species.
Realized Niche – In order to survive and avoid competition for the same resources, a species only
occupies part of its fundamental niche. Example- You may be capable of being president of a company,
but because of competition, you are vice-president.
Generalist and Specialist Species:
Generalist Species – Broad niches - a) live in many places
b) eat a variety of food
c) tolerate a wide range of environmental conditions
d) flies, cockroaches, mice, rats, white-tailed deer,
raccoons, coyotes, and humans
Specialists Species – narrow niches a) live only in one type of habitat
b) use only one or few types of food (problem?)
c) tolerate only a narrow range of climatic conditions
d) more prone to extinction
e) spotted owls, giant panda, polar bear, red-cockaded woodpecker
SPECIATION, EXTINCTION, AND BIODIVERSITY
A. Macroevolution – large scale evolutionary changes that lead to the
appearance of new species
1. Speciation – new species developed in response to changing environmental
conditions – sometimes called divergent evolution. Two species arise from one.
a. Takes place in two steps (mechanisms)
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Geographical isolation – physical barrier prevents two populations from interbreeding
Volcanic explosion, continental drift-land bridge, mountain
range, lake, road, Example –Arctic Fox
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Reproductive isolation- through mutation and natural selection, gene frequencies change
and the two populations can no longer interbreed. Do not produce live fertile offspring.
1. Patterns that affect speciation and extinction
Extinction : Two types
a) Background – a local environmental disaster occurs. Humans have become a
major force in background extinctions – local development and environmental
damage.
b) Mass – global event – widespread environmental damage (dinosaurs)
25 – 75% of the population is wiped out.
1. large scale movement of continents
2. gradual climate changes – due to continental shift- background extinction
3. rapid climate change due to some catastrophic event – mass extinction- ex dinosaurs
2. most species live for 4 – 22 million years – predict that 99.9% of all species that ever
lived are now extinct
3. Extinction of one species is an opportunity for another species
4. After mass extinction have periods of adaptive radiation -numerous new species
develop to fill available niches. Example - Darwin’s Finches
5. Biodiversity = Speciation – extinction
a. Extinction reduces biodiversity but creates new opportunities for speciation
b. Humans have become a force in premature extinction
c. Genetic engineering cannot replace lost species because we only rearrange what
genes are present.