life cycle summary
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Life Cycle Summary. YesYes Yes. YesYes Yes. YesYes Yes. NoYes Yes. YesNo Yes. YesNo Yes. NoYes Yes. Classically: A change in the relative frequencies of heritable traits within a population across generations Relative frequency: - PowerPoint PPT PresentationTRANSCRIPT
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Life Cycle SummaryDiploid Life cycle
Haploid Life cycle
Alternation of Generations
Mitosis?
Meiosis?
Fertilization
Mitosis after meiosis?
Mitosis after fertilization?
Multicellular diploid stage?
Multicellular Haploid Stage?
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
No Yes Yes
Yes No Yes
Yes No Yes
No Yes Yes
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Evolution: Classically: A change in the relative
frequencies of heritable traits within a population across generations
Relative frequency:
50% Tall plants 50% Short plants
55 generations later
25% Tall plants 75% Short plants
Modern: A change in the distribution of relative frequencies of genes (which code for heritable traits) within a population across generations
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Requirements for Evolution to occur:
Variation in traits [via genes (alleles)]
Heredity
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Darwin’s Observations Biogeography: species are distributed in
distinct clumps across the globe
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Biogeography: species are distributed in distinct clumps across the globe
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Fossils Evidence of organisms no longer present
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Evidence that many living organisms were not present in the past.
Today10,000 years ago
2 million years ago
5.5 million years ago
24 million years ago
34 million years ago
Moeri-therium
Bary-therium
DeinotheriumMammut (mastodon)
Platybelodon
Stegodon
Elephas maximus(Asian elephant)
Mammuthus(mammoth)
Loxodonta africana(African savannah
elephant)
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Agriculture: Selective breeding
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Agriculture: Selective breeding
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About 250 million years agoPlate tectonics
Plate movements and geological studies indicated the earth was older than the estimated 6,000 years
Figure 14.20
Mill
ions
of y
ears
ago
Cen
ozoi
cM
esoz
oic
Pale
ozoi
c
North AmericaEurasia
SouthAmerica
Africa
IndiaMadagascar
Antarctic Australia
Laurasia
Gondwana
Pangaea
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Economics: Competition for resources and the effects of overpopulation
Struggle for existence
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Evolution by Natural Selection (a mechanism of evolution) Population level:
If variation exists and If variation is heritable and If differential reproduction (differential selection) exists
Then over time, those variations that enhance the ablitiy of the organism to reproduce will increase in any population
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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
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The population size is small
Genetic drift – random fluctuations in the allele frequencies
Generation 1p (frequency of R) = 0.7q (frequency of r) = 0.3
Only 5 of 10 plantsleaveoffspring
Generation 2p = 0.5q = 0.5
Only 2 of10 plantsleave offspring
Generation 3p = 1.0q = 0.0
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Gene flow
Immigration or emigration occurs based on the trait
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Sexual Selection
Mating is non-random in the population with respect to the trait
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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.
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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
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Example: Marine Iguana
Adaptations do not have to be one trait, they can be a suit of traits
“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:
Reduce blood flow to body surface- helps retain heat
Lower metabolic rate – conserves O2
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Adaptation refers to traits that are heritable Acclimation: Changes in the structure or physiology of an individual
over its lifetime
Examples: Increasing muscle mass via weightlifting
High altitude acclimation:
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Organizational level evolution occurs? 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)