1. Evolution and Biodiversity: Origins, Niches, and Adaptation
Chapter 5
Evolution and Biodiversity:
Origins, Niches, and Adaptation

2. The Origin of Life How did life emerge on Earth?
Chemical analysis and radioactive elements in rocks and fossils
Simple inorganic compounds formed amino acids (proteins), simple sugars (carbs) and DNA/RNA

3. Most widely-accepted hypothesis
Organic molecules needed for life came from inorganic chemicals in the Earth’s atmosphere
-energy from lightning
-heat from volcanoes
-intense UV light
-other forms of solar radiation

4. Scientific Experiments
Since 1953
Placed mixtures of gases (in early atmosphere) into closed containers
Subjected gases to sparks (lightning) and heat
Building blocks (necessary for life) formed

5. Electrode Water vapor Condenser
H2O
Electrode
CH4
Water vapor 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

6. Are there other possibilities?
Organic molecules formed from…
Dust particles in space that reached earth on meteorites or comets
Deep within the earth
Hydrothermal vents (cracks in ocean floor, lead to chambers of molten rock)

7. REGARDLESS…
Organic molecules accumulated and underwent chemical reactions for several hundred million years
Led to formation of proteins, RNA, and other polymers that formed protocells
Protocells could take up materials from environment, grow, and divide

8. Earth Developed in 2 Phases
Chemical evolution: organic molecules and chemical reactions to form protocells
-1 billion years
Biological Evolution: single-celled prokaryotes  single-celled eukaryotes  multicellular organisms
-3.8 billion years

9. © 2004 Brooks/Cole – Thomson Learning
Formation
of the
earth’s
early
crust and
atmosphere
Small
organic
molecules
form in
the seas
Large
First
protocells
Single-cell
prokaryotes
eukaryotes
Multicellular
organisms
form, first
in the seas
and later
on land
© 2004 Brooks/Cole – Thomson Learning
Chemical Evolution
Biological Evolution

10. How do we know what organisms lived in the past?
Fossils!: mineralized or petrified replicas of skeletons, bones, teeth, shells, seeds, etc.
Physical evidence of organisms
Internal structures
Fossil record is incomplete!
We have 1% of species believed to have ever lived!

11. What is Evolution?
Evolution: The change in a population’s genetic makeup (gene pool) through successive generations
Theory of Evolution: all species developed from earlier, ancestral species

12. Macro- and Microevolution
Microevolution: small genetic changes that occur in a population
Macroevolution: long-term, large-scale evolutionary changes through which…
1. new species are formed from ancestral species
2. other species are lost through extinction

13. Remember… Genetic information in chromosomes is contained in DNA
Genes (on chromosomes) represent certain traits that may be passed to offspring
Gene pool: set of all genes in individuals of a population
Alleles: different forms of a gene
(dominant or recessive)

14. Mutations
Genetic variability originates through mutation: random changes in the DNA in a cell.
Mutations happen in two ways:
DNA is exposed to radioactivity, X-rays, mutagens
Random mistakes when DNA is copied (cell division)
 Sometimes, mutations are beneficial

15. Microevolution
Microevolution: change in a population’s gene pool over time
Summary of microevolution: genes mutate, individuals are selected, populations evolve
Camouflage; white was prevalent. During industrial revolution (England), soot and pollutants darkened trees and lichens…dark form became common

16. Natural Selection
Occurs when individuals have traits that increase their chances of survival
Needs 3 conditions:
Natural variability for a trait
Trait must be heritable
Must lead to differential reproduction (individuals with trait leave more offspring than individuals without trait)

17. Let’s think about the moths again…
Variability: 2 color forms
2. Heritability: color form was genetically-based
3. Differential reproduction: greater survival and reproduction by one color

18. When environment changes…
Population may:
Adapt to new conditions through natural selection
Migrate to an area with better conditions
3. Become extinct

19. 3 Types of Natural Selection
Directional: changing environmental conditions select individuals who are not the norm so that their type makes up more of the population (“it pays to be different”)
Stabilizing: gets rid of individuals on both extremes (“it pays to be average”)
Diversifying: favors individuals with uncommon traits and reduces average individuals (“it does not pay to be normal”)

20. 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

21. 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

22. 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

23. Coevolution
Changes in the gene pool of one species leads to changes in gene pool of the other
Example: plants evolve defenses (camouflage, thorns, poison) effective against herbivores
Herbivores evolve immunity against these traits

24. Ecological Niches
Niche: role of a species in an ecosystem (like an occupation)
Habitat: physical location (like an address)
2 types of niches:
Fundamental niche: potential and theoretical niche (without competition, etc)
Realized niche: actual niche

25. How do new species evolve?
Speciation: two species arise from one
Geographic isolation: groups of the same population become physically separated and undergo different evolution
Ex. mountain range, volcano, earthquake
 Leads to reproductive isolation

26. Different environmental conditions lead to evolution
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 evolution
into two different species.
Southern population
Northern population
separates
Early fox
population

27. 135 million years ago 225 million years ago 65 million years ago
PANGAEA
LAURASIA
120°
80°
40°
80°
120°
120°
80°
80°
120°
GONDWANALAND
135 million years ago
225 million years ago
NORTH AMERICA
EURASIA
AFRICA
120°
80°
120°
120° 0°
40°
120°
INDIA
SOUTH
AMERICA
MADA-
GASCAR
AUSTRALIA
ANTARCTICA
65 million years ago
Present