Transcript evolution - TeacherWeb

Connect these two together!
Earth: Just-right, Resilient
Planet
Temperature
0-100
Liquid water
Orbit-right distance
Rotation/Tilt
Size and gravity
Ozone layer-bacteria
DO NOT POST TO INTERNET
Fig. 5-1, p. 92
Life has been around for 3.7
billion years
• Avg. surface temp. has been between
50-68o
• Even with a 30-40% increase in the
sun’s output
EVOLUTION & BIODIVERSITY
Chapter 5

Origins and Early Evolution of
Life
Chemical evolution
 Biological evolution
Fig. 5-2 p. 93
How did life evolve?
a. Two Hypotheses of Evolution:
1) Chemical Evolution - @ 4.7 billion years ago, lasted
1 billion years
Formation of early molecules  small proteins 
large proteins  complex organic molecules  first
protocells
2) Biological Evolution – started 3.7 billion years ago,
up to present
Single-celled Prokaryotes  Single-celled Eukaryotes
diversification  multicellular organisms in sea
then land
b. Types of Evolution
1) 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
ex. peppered moths
2) Macroevolution
Long-term, large-scale
changes in organisms.
Usually involves major
changes among groups of
species (development of
new genera) ex. horses
Modern humans
(Homo sapiens)
appear about
2 seconds
before midnight
Biological
Evolution Over
Geologic Time
Age of
mammals
Age of
reptiles
Insects and
amphibians invade
the land
midnight
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
Fig. 5-3, p. 94
Recorded human
history begins
1/4 second
before midnight
A. Evolution
1. Species Theory
• What is a species?
– Two populations of sexually
reproducing organisms can be
considered separate species if they
cannot interbreed (or are reproductively
isolated)
What is a species?
• Distinct type of organism
–physically similar
–can produce viable offspring
–biochemical traits
–DNA
–behavioral (least efficient)
2. Evolution
• What two things are needed for
evolution to occur?
-time
-death
1) Microevolution works through a combo of
processes that change genetic makeup of a
population:
a) Mutation - random changes in DNA structure
or number in a cell
-external and internal
b) Natural Selection - some populations have
traits that cause them to survive and produce
offspring more than others
c) Gene Pool – set of all genes in a population
that reveals the change.
Page 109
Microevolution, continued
e) Differential reproduction – organisms
best adapted to a given environment will
be most likely to survive to reproductive
age and have offspring of their own.
3. Natural Selection
Definition - nonrandom breeding of
individuals where the individuals that
have the highest reproductive success
are those that are most suited to the
environment
Types
a) Directional
b) Stabilizing
c) Diversifying
a. Directional Selection
• Individuals from just one
side of the distribution
reproduce
• population looks different
over time
• mean changes
• range does not change
b. Stabilizing
Selection
• Individuals from the center
of the distribution are the
only ones to reproduce
• individuals look more
similar over time
• mean does not change
• range narrows
• animation
c. Diversifying Selection
(AKA Disruptive selection)
• Individuals from the ends of
the distribution are the only
ones to reproduce
• produced 2 separate
phenotypes
• mean does not change (but
few individuals at mean)
• range increases
• animation
4. Co-evolution- Occurs when populations of
two different species interact over a long
time, changes in the gene pool of one
species can lead to changes in the gene pool
of the other species.
B. ECOLOGICAL NICHES
– Range of tolerance of enviro
– Resource use
1. Niche Breadth
a. Fundamental niche is the full potential
range of physical, chemical, and biological
conditions and resources it could
theoretically use if there were not direct
competition from other species
b. Realized niche- a species usually
occupies only part of its fundamental niche
in a particular community or ecosystem
Herring gull is a
tireless scavenger
Black skimmer
seizes small fish
at water surface
Flamingo
feeds on
minute
organisms
in mud
Scaup and other
diving ducks feed on
mollusks, crustaceans,
and aquatic vegetation
Brown pelican dives for fish,
which it locates from the air
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
insects, and seeds
Louisiana heron wades into
water to seize small fish
Dowitcher probes deeply
into mud in search of
snails, marine worms,
and small crustaceans
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Knot (a sandpiper) picks up
worms and small crustaceans
left by receding tide
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Adaptation
• Adaptation - heritable trait that enables
organisms to better survive and
reproduce under a given set of
environmental conditions (competitive
advantage)
1. What are the limits to
adaptation?
a. Limited genetic variability in
population – traits must already
exist in gene pool
b. Reproductive capacity and time
delays
c. Most of population must die or not
reproduce for desirable trait to become
dominate and be passed on
Misconceptions About Evolution
• “Survival of the fittest” means “survival
of the strongest” – fitness is a measure
of reproductive success
• Evolution involves a grand plan of
nature where species become more
perfect – there is no plan or goal
D. How do New Species Evolve?
2. Speciation - two species arise from one.
a. Geographic isolation - physically separated
(mountains, water)
b. Reproductive isolation - when mutation
and natural selection operate independently
in two geographically isolated populations
and change the allele frequencies in
different ways. Process is called divergence
 divergent evolution
What determines biodiversity?
Biodiversity = Speciation - Extinction
(number of species
on the planet)
creation of new
species
removal of
species
4. Extinction
- The elimination of all individuals in a species from
the earth
a. Two major types:
1) Background extinction rate - relatively constant
rate of extinction in the fossil record
–
–
average lifespan = 4 million yrs
extinction = 3-30/yr
2) Mass extinction - major loss of species
– climate change, humans, catastrophic events
–
–
average lifespan - thousands of years
extinction = thousands/yr
Chicxulub Crater – 112 miles wide, 3,000 feet deep
LAURASIA
120°80°
40° 80° 120°
120°80°
GONDWANALAND
80° 120°
135 million years ago
225 million years ago
EURASIA
AFRICA
120°80°
120°
120°
0°
MADAGASCAR
65 million years ago
Present
40°
120°
b. Adaptive Radiation –
extinctions open up gaps in
niches so new species can
evolve to fill niches
b. Adaptive Radiation – after
a mass extinction, over the
next 10 million years, new
species evolve to fill in
new or abandoned niches
How do we affect extinction
rates?
1) Simplify ecosystems (monocultures/disturbed
habitats)
2) Strengthening pest populations (resistance to
pesticides)
3) Eliminating predators (can create new pests)
4) Introducing new species (starlings)
5) Over-harvesting
6) Interfering with chemical cycling and energy
flow (UV/ozone, heat pollution)