Midterm 1 Flashcards
Evolution
• many definitions are available
• in a succinct way, it could be defined
as “descent with modification”
• more technically:
an outcome of evolutionary processes that
generate change (e.g. natural selection) and
evolutionary patterns that constrain that change
(e.g., phylogenetic history).
Charles Darwin’s Theory of Evolution
by Natural Selection
The ideas of this person had a major influence on
biology and the evolutionary framework for the study
of animal behavior
Concept of Evolution
All living things have descended from
common ancestors by a natural historical process of change and diversification.
Evolutionary change occurs if three
conditions are met:
- Variation
- Heredity
3) Differences in reproductive success
Variation
- members of a species differ in some of their
characteristics
Heredity -
parents are able to pass on some of their distinctive
characteristics to their offspring
Differences in reproductive success
- some individuals have
more surviving offspring than others in their population,
thanks to distinctive characteristics
Darwin’s Three Key Concepts
of Evolution:
- Adaptation
- Descent with Modification
- Natural Selection
Adaptation
= a positive characteristic of an organism favored by the
process of natural selection, where
-favorable (heritable) traits produce more surviving offspring
than others in their population.
-Characteristics of a species are adapted to its ecological niche
Mimicry = look like your background or something other than what
you are.
• Mimicry as example:
Defensive mimicry - for the purpose of avoiding or escaping from your predators.
Aggressive mimicry -*Adaption
for the purpose of capturing prey.
Descent With Modification
Refers to the passing on of traits from parent
organisms to their offspring (aka, heredity)
• Any 2 species can be traced back ultimately to a common ancestor.
• Thus the more recent their common ancestor, the more similar two
species should be.
• Also, the more similar their history
of adaptations, the more
similar two species should be
Darwin’s Tree of Life 1837
• The differences between them are the result (in part) of adaptations
Homology
-similarities due to recent common ancestry
-Homologous traits in different animals are similar because they are
derived from a common ancestor.
-Example of homology:
Bones of mammalian forelimbs are homologous
to forelimbs of human, horse, seal, bat, kangaroo,
mole etc.
The forelimb bones have different functions but
share a the same identifiable sequence and
arrangement of bones
Analogy
= similarities due to similar function
-Analogous traits in different animals are similar because
they are adaptations to a similar ecological niche.
If you trace back to the common ancestor of the animals, it would not have that trait.
–Example of Analogous traits (analogy)
Body shape and flippers are analogous in seals and penguins.
Designed for locomotion through water, but underlying structures are very different.
**Divergent vs. Convergent Evolution
DIVERGENCE
occurs when two evolving groups of recent common
ancestry become more dissimilar.
Convergence
**Divergent vs. Convergent Evolution
occurs when two evolving groups of distant common
ancestry become more similar.
Natural Selection (definition) -
Differential reproduction and survivorship
among individuals within a population. The
mechanism that results in adaptive evolution.
Natural (direct) Selection
• Individuals vary within a species
• Variation is (in part) heritable
• If individuals vary on some trait related to
reproductive success, the better adapted
individuals will leave moreoffspring.
• Natural selection occurring over a long time
will lead to dramatic changes in a species
(evolution).
Some qualifications of natural selection:
• If there is no genetic basis of variation in a trait,
then no natural selection of that trait will occur.
• Reproductive success (not survival) is the bottom line for
natural selection.
• Selection acts on individuals
- not species, groups, or populations
- traits are not present for the “good of the species”
However, many behaviors appear to benefit the group at the
cost to the individual: they are altruistic
Altruism
an individual acts to further the reproductive success of another individual(s) at some reproductive cost to itself
hypothesis
is simply a logical, testable
explanation for a specific set of observations
that serves as the basis for experimentation.
Scientific Method
observation, formulating a hypothesis, making
predictions, experimenting to test the predictions and
drawing conclusions.
Prediction vs Hypothesis
“We hypothesized that, owing to its effects on the frontal lobe and hippocampus, alcohol consumption would impair long-term memory.”
“We predicted that subjects who drank 6 or more ounces of alcohol would recall significantly fewer”
Application of Darwinian theory:
When trying to understand ultimate reasons for animal
behavior, biologists try to come up with a hypothesis that
is consistent with natural selection theory
-In some case certain traits (or behaviors) might not seem to increase an individual’s reproductive success (or do they?).
EXAMPLE: Monkey killing other babies to make their own video thing called infanticide
Hanuman langur monkeys
Behavior • They live in groups of 11-64, typically 1 male:multi-female • langurs spend up to 80 per cent of their time on the ground, although will some spend time in the trees. • are diurnal and move quadrupedally. -Males fight to monopolize reproduction with the females in the group -When a new male takes over a troop, he systematically kills all the infants sired by the previous alpha male.
1) Social pathology hypothesis for infanticide in Langur moneys
infanticide is an abnormal, pathological response to overcrowding in areas where they are fed by humans. Non-evolutionary
If this hypothesis were true, then one would expect to see
infanticide by males only in areas where langurs live in
very high densities. Results don’t support this.
