Download Evolution- Mechanisms of Evolution

Evolution- Mechanisms of
Evolution
Biology
Miami Arts Charter
Introduction
- change in the heritable characteristics of biological populations over successive
generations
- Gives rise to biodiversity
- https://www.youtube.com/watch?v=GhHOjC4oxh8
Contributions
-
Lyell:
Malthus: overpopulation and resources
Lamarck: Acquired traits
Wallace: also suggested that evolution of species was caused by this natural
selection
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suggested that evolution of species was caused by this natural selection
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Cowrote paper: On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and
Species by Natural Means of Selection
Lyell
- Wrote Principles of Geology
- one of the first to believe that the world is older than 300 million years based on
geological anomalies
- idea of uniformitarianism, that the earth was shaped entirely by slow-moving
forces still in operation today, acting over a very long period of time
- Stratigraphy: studying the layers which would become the different time periods
in the history of the world
-
Tertiary period into three parts, which he named the Pliocene, Miocene, and Eocene. He also
renamed the traditional Primary, Secondary and Tertiary periods (now called eras) to
Paleozoic, Mesozoic and Cenozoic
Malthus
-
An Essay on the principles of population
Population growing exponentially
Food grew linearly
Lack of resources would lead to famines and death
Would unfairly affect the poor
Lamarck
-
early 19th Century
a French naturalist
theory for how evolution works
Lamarckism
-
proposed that organisms inherited changes caused by use or disuse in its parents.
-
For example, if a parent giraffe stretches its neck to get at leaves on tall trees, its descendents are
born with longer necks, and so giraffes evolve over generations to have long necks
Darwin
- English naturalist and geologist
- Decent from a common ancestor
- Branching pattern of evolution resulted from Natural Selection
-
Struggle for existence
Explains the diversity of life
Basic mechanism of evolution
- On the Origin of Species by Means of Natural Selection, or the Preservation of
Favoured Races in the Struggle for Life: 1859
- Widely accepted by 1870
Natural Selection
- Unequal survival and reproduction of organisms due to environmental forces,
resulting in the preservation of favorable traits
- 4 principles
- 1. Variation
-
Mutations
Meiosis
- recombination due to crossing-over in 1st division
- random movement of chromosomes in 2nd division
- Random sex cell selection & fertilization
- 2. Differential Reproduction
-
Environment cannot support unlimited population
-
Certain phenotypes Traits that are well adapted for the environment are more likely to survive and
reproduce
- Non-random mating
Natural Selection
- 3. Heritability
-
Traits need to be passed onto future generations through genes
- 4. Result is descent with modification
- When humans select the modification = artificial selection
- When the environment selects = Natural Selection
How Natural works
Natural Selection is Survival of the
fittest (REPRODUCTION)
There is no agent involved in natural selection.
Natural selection is a process of elimination
Selection pressure on a population?
•Competition for food
• Competition for a mate
• Changes in the environment
• Predators
• Parasites
Examples of Selection Pressures
Predators - variants with adaptations allowing them to escape predators have more
offspring
- e.g. speed, defensive weapons, camouflage, mimicry
Prey/Food - variants with adaptations allowing them to obtain food have more
offspring
- e.g. Speed, senses for finding prey/food, weapons for killing prey or obtaining
food, camouflage for stealth
Climate - those who can survive new climate best have more kids
- e.g. ice age, change in climate due to migration.
Mates - variants with adaptations allowing them to attract a mate to have offspring
- e.g. strong, attractive, good provider
Predation pressure
•Only the darker colored moths survived after
the industrial revolution. Selection was for
more melanin.
Food
EXAMPLE
- The neck of the Giraffe
- Co-evolution with Acacia Trees
- Selection pressure is source of food
- The Red Queen Hypothesis...
Types of Selection
- Directional Selection
- Natural selection favors one extreme of the population
for that trait
- often happens when environment changes in a
consistent way- e.g.climate gets colder.
Types of Selection
- Disruptive Selection
- Causes species to diverge
- Stabilizing Selection
- Natural selection favors the average for population
selected
- Sexual Selection
Directional Selection
-
Neck of a giraffe
Moth color
Antibiotic resistant bacteria
Camouflage and mimics
Sexually selected traits
Stabilizing Selection
- When the extremes of the trait aren’t as well suited
- Examples
-
bird clutch size
Tail length in birds
-
Child birth weight
Disruptive Selection
- Causes divergence within the species
- Occurs when two different types of resources in one
area
- Results in specialization for each branched group
- May lead to formation of new species
- E.g. Darwin’s Finches
- May have been how the divergence of sexes occurred
Camouflage, Mimicry, & Decoys
Purpose - escape from predators, sneaking up on prey
Camouflage - directional selection favors individuals who most resemble the
environment
Mimicry - directional selection can favor individuals that most resemble something
harmful, unappetizing, or non-threatening
Decoys - directional selection can favor individuals that use lures or decoys to attract
other animals to be eaten or help them unwittingly