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.
2) Quicker reproduction hypothesis for infanticide in Langur moneys
infanticide boosts
reproductive success of new dominant male.
When lactating infant is killed, its mother might resume her
reproductive cycle sooner and thus become impregnated
sooner by the new dominant male.
Evolutionary – individual selection.
Does evidence support Quicker reproduction hypothesis?
• Infanticide should occur soon after takeover
• Females who have lost their infants will promptly resume
cycling and become sexually receptive to the killer male.
• Killer male will not kill any of his own young.
• Infanticide is not dependent on group size or density.
Evidence exists to support all of the above predictions.
1) Cannibalism Hypothesis
- this hypothesis predicts that infanticide should occur
soon after a take over when dominant male is energetically stressed and need to reproduce quickly - is there data to support this hypothesis? NO
2) Population Regulation Hypothesis
- this hypothesis predicts that male langurs commit infanticide as means of population regulation.
E.g., High density populations put stress on food supply
resources. Infanticide would then prevent overpopulation
Who benefits?? Group benefits but not the male killer!
This is not Darwinian selection…..
Darwinian selection
= based on differences among individuals
and their reproductive success
Group selection
based on differences among groups and
their ability to survive.
George Williams (1966)
challenged the concept of group selection
in this book Adaptation and Natural Selection
- Main point: Williams showed that survival of alternative alleles was
much more likely to be determined by differences in the
reproductive success of genetically different individuals than by
survival differences among genetically different groups.
Tinbergen’s Levels of Analysis
• The causes of any behavior can be understood at
four levels of analysis
“Ultimate”
*Level of analysis
phylogeny & function
-Evolutionary history
“Proximate”:
*Level of anaysis
development & immediate causation
-Within the lifetime only
Tinbergen’s Four Questions (levels of Analysis)
1) What is its function?
(Effects on lifetime reproductive success ) ***ULTIMATE
2) How has it evolved? (long term Qs)
(evolutionary origins)
3) What causes it?
(sensory-motor mechanisms/ hormone systems) **Proximate
4) How does it develop? (immediate)
(genetic mechanism/ontogenetic processes)
Tinbergen’s four questions
1. What is the survival value or function of a
behavior?
2. What is the cause(s) of a behavior?
3. What is the development of a behavior?
4. What is the evolutionary history of a
behavior?
Four answers to the question
1. To attract mates to breed.
2. Increasing day-length changes hormone levels
3. Birds have learned to sing from their neighbors
4. Bird song has evolved from simpler songs
in ancestral bird species.
Classical Roots of Ethology
Animal behavior interests date back to
prehistoric times
Aristotle (384-322 B.C.)
• often considered to be the father of biology
& psychology
• classified > 540 species of animals; segregated as
vertebrates (“enaima”) or invertebrates (“anaima”) based
on the presence or absence of blood.
• produce the first systematic account of animal
behavior (Historia Animalium)
• proposed the concept of scala naturae (“natural
ladder”) to explain a gradual transition from
inanimate to plants, animals, and humans.
Historia Animalium
• Species’ habitats
• Animal behaviors
(e.g., foraging & social behavior of bees,
migratory behavior of cranes & pelicans,
electric discharge of electric rays,
brood parasitism by European cuckoos)
• Relative grades of animal intelligence
scala naturae
Aristotle’s concept of scala naturae became closely intertwined with our view of God and religion. (compatible with the Biblical view) Scala naturae was seen as logically ending with God as the ultimate expression of perfection.
The Great Chain of Being
Medieval Concept of God’s strict & hierarchical structure of the universe Ranked animals by level of development Lowest forms at bottom Humans near the top
- *Pre-Darwinian Roots 17th and 18th century
1. Aristotelians
- distinguished human soul
(vs. animals which do not have souls) - Humans are rational and use logical reasoning
- Animals are guided by sensory perception
- *Pre-Darwinian Roots 17th and 18th century
2. Cartesians (Based on Descartes)
• Shared Descartes concept of Mind-body
Dualism
- maintained that humans are unique from
animals because of their ability for mental
experience (mind).
• Subscribed to Descartes’ mechanical theory of Animal
Behavior (inspired by moving statues in the gardens of the
Saint Germain palace).
Descartes concept of Mind-body
Dualism
- maintained that humans are unique from
animals because of their ability for mental
experience (mind).
Descartes’ mechanical theory of Animal
Behavior
(inspired by moving statues in the gardens of the
Saint Germain palace).
-Descartes conceived animals as complex
“moving statues” equipped with finer tubes
and faster & lighter fluids called “animal sprits”
-• Thus, they maintained that animals (w/ no soul
or free-will) operated as mere machines or
brutes and followed the rules of physics
- Sensationalists
Major Influence from John Locke (1600’s)
- tabula rasa - “blank or erased tablet” Born with blank slates and everything in life is learnt
-“All ideas come from sensation or reflection.”
- believed animals and humans were born with a tabula rasa
- it is the learning process that determines what is “on the
tablet”
Humans knowing draw from same resources
as those available to animals
Stressed the role of environment & experience
Summary of Contrasts between Aristotelians/Cartesians
and Sensationalists
Aristotelians/Cartesians 1. Dichotomy* between humans as reasoning beings with souls and animals as automata. 2. Complex behavior explained by instincts instilled by God. 3. Innate tendency of species type
VS.
Sensationalists 1. Humans respond to environment like animals 2. Downplayed instincts, emphasized acquired knowledge 3. Agnostics/atheists 4. Environmental effects on individual
Cartesian Dilemma
It was clear that the ‘beast machine’ image of
animals was not correct because animals clearly
could perceive, feel, and act intelligently as no
machine could
• Led to new dichotomies…
Dichotomies
Humans as rational beings
vs.
Animals as beast-machines
Instinct or Nature vs nurture
vs.
Learning
Darwin’s Evolutionary Framework
-The Origin of Species (1859) – general theory
of evolution by natural selection.
-Natural Selection
-Darwin suggested that:
• all organisms were inter-related
• different organisms (including humans!!) were derived
or evolved from common ancestors
Natural Selection =
process of differential
reproduction and survivorship among
individuals within a population that lead to the
adaptive evolution of traits (behaviors).
Darwin’s theory
marked the split between biology & religion
Interests shifted from cataloging biological diversity for the
clarification of God’s plan to the questioning of how
biological diversity arose
Darwin’s Origin of Species
did not focus not on animal behavior, but provides
conceptual framework for the field of
animal behavior
Later in life Darwin…
Later publishes two books which apply his
evolutionary theory to behavior:
The Descent of Man and Selection in Relation
to Sex (1871) and Expression of the Emotions
in Man and Animals (1872)
-Placed humans on the same mental
continuum as animals
Darwin’s principle of antithesis
Darwin was first to observe that instincts could
often be grouped as pairs of opposites
Antithesis Principle
signals with opposite meanings (aggression vs. submission)
should have opposite or contrasting form to make meaning clear
Darwin on Instinct
Both innate and acquired
-Instincts congenitally expressed (When fully developed, chick pecks/cracks egg shell to escape)
-Instincts change little through life
of organism
-Tongue-flick behavior of chameleon doesn’t change
Roots of Comparative Psychology
George John Romanes (1848-1894)
• 19th century naturalist
• a protégé of Darwin
• coined the term and laid the foundation of
“comparative psychology”
• He also postulated that Primary instincts arose through
natural selection and Secondary instincts were derived
from learned behavior
• further developed the idea of mental continuum and
postulated a similarity of cognitive processes and
mechanisms between humans and animals
-Based on subjective observations
-the evolutionary appearance of emotions in animals
C. Lloyd Morgan
-British psychologist
- author of the first textbook on
Comparative Psychology (1894)
- best remembered for his experimental
approach to animal psychology now known as
“Morgan’s Canon” (special form of Occam’s Razor)
“Morgan’s Canon”
-helped stop the anecdotal tradition, thereby
helping comparative psychology to become the objective
science that is today
-when two explanations for a behavior
appear equally valid, the simpler one is preferred.
20th Century: The development of two approaches
to the study of animal behavior
-1) Classical Ethology Approach:
- focused on the evolution and function of inherited and innate behaviors - European school of animal behavior - was descriptive and field-oriented - gave rise to the establishment of ethology as a new and independent discipline (between the 1930s and 1950s) by the two founding fathers of ethology:
Konrad Lorenz (1903-1989)
Austrian animal behaviorist
• An early interest in natural history and evolution
• Medical training: comparative anatomy & embryology
• Oskar Heinroth (comparative studies of the behavior of ducks)
First to introduce the term “ethology” (from Greek word ethos meaning
“manner” or “behavior”) to describe the analysis of natural behavior.
• considered to be one of the co-founders of ethology
• studied instinctive behavior in animals,
especially in greylag geese and jackdaws
• recognized behavior as an inherited trait, used for
taxonomy and phylogenetic analysis.
Social imprinting in Geese
Konrad
working with geese, he rediscovered the
principle of imprinting (originally reported by Douglas Spalding in the 19th century)
Best known form is filial imprinting - young
animal learns the characteristics of its parent
Imprinting = any kind of phase-sensitive learning
that is rapid and apparently independent of the
consequences of behavior.
