Transcript Life Cycle Summary

Life Cycle Summary
Diploid Life
cycle
Haploid Life
cycle
Alternation of
Generations
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Mitosis after
meiosis?
No
Yes
Yes
Mitosis after
fertilization?
Yes
No
Yes
Multicellular
diploid stage?
Yes
No
Yes
Multicellular
Haploid Stage?
No
Yes
Yes
Mitosis?
Meiosis?
Fertilization
Evolution:
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Classically: A change in
the relative frequencies
of heritable traits within a
population across
generations
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Relative frequency:
50% Tall plants
50% Short plants
55 generations later
25% Tall plants
75% Short plants
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Modern: A change in the
distribution of relative
frequencies of genes
(which code for heritable
traits) within a population
across generations
Requirements for Evolution to occur:
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Variation in traits [via genes (alleles)]
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Heredity
Darwin’s Observations
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Biogeography: species are distributed in
distinct clumps across the globe
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Biogeography: species are distributed in
distinct clumps across the globe
Fossils
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Evidence of organisms no longer present
Evidence that many living organisms
were not present in the past.
Loxodonta africana
(African savannah
Elephas maximus
elephant)
(Asian elephant)
Today
10,000 years ago
2 million years ago
Mammut (mastodon) Stegodon
Deinotherium
5.5 million years ago
24 million years ago
Moeritherium
Bary-therium
34 million years ago
Mammuthus
(mammoth)
Platybelodon
Agriculture: Selective breeding
Agriculture: Selective breeding
Plate tectonics
Cenozoic
About 250 million years ago
Eurasia
India
South
America
Laurasia
Mesozoic
Plate movements and
geological studies
indicated the earth
was older than the
estimated 6,000 years
Paleozoic
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Madagascar
Antarctic
Millions of years ago
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Africa
Figure 14.20
Economics: Competition for resources
and the effects of overpopulation
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Struggle for existence
Evolution by Natural Selection
(a mechanism of evolution)
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Population level:
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If variation exists
and
If variation is heritable
and
If differential reproduction (differential
selection) exists
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Then over time, those variations that
enhance the ablitiy of the organism to
reproduce will increase in any population
Mutation occurs in the trait

Mutation directly changes gene frequencies
An example of a spontaneous
mutation during the development of
plant leaves
For evolution to occur via this
mechanism, what has to be true of
the mutation?
The mutation has to be
heritable
The mutation of fruit flies with four
wings is an inherited mutation
The population size is small
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Genetic drift – random fluctuations in the
allele frequencies
Only
5 of
10
plant
s
leave
offspr
ing
Generation 1
p (frequency of R) = 0.7
q (frequency of r) = 0.3
Only 2
of
10
plants
leave
offspri
ng
Generation 2
p = 0.5
q = 0.5
Generation 3
p = 1.0
q = 0.0
Gene flow

Immigration or emigration occurs based on
the trait
Sexual Selection

Mating is non-random in the population with
respect to the trait
Which mechanism leads to adaptation
to the environment?

Natural selection: Adaptations are traits that
increase the probability that an organism will
survive and reproduce in the current
environmental conditions.
What is an adaptation?

A heritable characteristic of an organism
that helps it to survive and reproduce in a
particular environment.
Mimicry of a
poisonous animal
will increase the
probability of survival
and survival until the
organism is able to
reproduce
Example: Marine Iguana
Adaptations do not have to be one
trait, they can be a suit of traits
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“The guanas are small, and of a sooty black, which, if
possible, heightens their native ugliness. Indeed, so
disgusting is their appearance, that no one on board could
be prevailed on, to take them as food.” Captain James
Colnett (1798)
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Flattened tail – aids in swimming
Salt gland – Allows drinking of salt water
Long, sharp claws – Aid in clinging to rocks
Diving adaptations. While diving they:
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Reduce blood flow to body surface- helps retain
heat
Lower metabolic rate – conserves O2
Adaptation refers to traits that are heritable
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Acclimation: Changes in the structure or
physiology of an individual over its lifetime
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Examples:
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Increasing muscle
mass via weightlifting
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High altitude acclimation:
Organizational level evolution occurs?
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Living organisms display a natural
hierarchy of organization and
emergent properties that are more
than the simple sum of their parts
Atoms lead to
Molecules, which lead to
Organelles, which are arranged
within
Cells, which make up
Tissues, which make
Organs, which form
Organ systems, which together
make an
Organism, which is part of a
Population within a
Community in an
Ecosystem, the largest of which is
the
Biosphere (=Earth)