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Chapter 3

chapter 3

Course Code
Ingrid L.Stefanovic

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Chapter 3: Evolution heredity and behaviour
The development of evolutionary theory
Heredity and genetics
Humans and evolution
The development of evolutionary theory
-Understanding behaviour requires to learn about both proximate and ultimate
causes of behaviour
Biological evolution- Changes that take place in the genetic and physical characteristics
in a population or group of organisms over time.
-Darwins concept, argues that over time organisms originate and become adapted to
their environment by biological means
-Became the dominant aspect of psy in North America
Adaptive significance- the effectiveness of behaviour in aiding organism to adapt to
changing environmental conditions
Evolutionary psychology- new subfield of psych that studies how evolution and genetic
variables influence adaptive behaviour
Ultimate causes-(Latin- ultimatus to come to an end”) evolutionary events and conditions
throughout the generations that have slow shaped our behaviours through time
Proximate causes- (Latin- proximus near”) immediate environmental and condition
variables that affect behaviour
Culture- sum of socially transmitted knowledge, customs and behaviour patterns common
to a particular group of people
For instance, in Psych P.O.V, how thinking and behaving shape cultural adaptations
to changing environmental conditions
John la-mark -18th century- proposed environment responsible for structural
changes in plants n animals ex: changes in structural characteristics, when they
catch prey
-inheritance of acquired characteristics
Herbert Spencer- came after la-mark; liked his idea; social Darwinism, thru
evolution separation occurs but systems become more complex; human brains
evolves and changes + progess.
-Introduced orderly evolution- believed that evolution had purpose, to seek
pleasure+ avoid pain known as Spencer Bain Principle
Darwin- 1809-82
-Doesnt believe in pain and pleasure accidental variation, parents couldnt
choose characteristics, it just randomly happened. NO purpose, or direction
-Features that help survival are not only necessary but helpful to survival in a
given environment.

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The Voyage of the Beagle
-Darwin had a friend he met at Christs College who gave up his opportunity and gave it to
Darwin- to be an unpaid naturalist and travelling for 5 years on the HMS Beagle boat
which ended in 1836
- Graduated with a degree in theology in England 1831
- The mission of the Beagle, was to explore and survey the coast of South America and to
make hydro graphic measurements worldwide
- observed the plants, flowers, and fauna of south America, Australia, south Africa, and
islands of pacific, south Atlantic and Indian oceans, Galapagos islands off the west coast of
south America
- the creatures and objects that he collected were sent to England throughout the trip which
were later examined by naturalists from all over Europe
The origin of species- published in 1859
Artificial selection- procedure which specific animals are used to mate with another to
produce off springs that posses desirable characteristics
-Darwin bred pigeons for a while, in which led to his new assumption: if artificial
selection can produce such different varieties of pigeons, could a similar process
result in different species?
-This led him to develop the idea of biological evolution which explains how genetic
and physical changes occur in groups of animals over time
Natural selection- the consequence of the fact that because ther are physical and
behavioural differences among organisms, they reproduce differently. ex, some
animals who are the survivors may produce more off springs than other animals, occurs
among off spring babies.
Based on accidental variation and competition
Therefore, natural selection is the primary element of biological evolution
Alfred Wallace, also came up with the principal of natural selection
Both Darwin and Wallace were inspired by the book population by Malthus
Made a joint presentation- each lay equal claim of the theory and Darwins abstract
today is known as Origin of Species”
Evolution can be put into 4 insights
1.Species are not fixed, but rather change over time
2.Evolution is a branching process- all species descend from a single common ancestor
3.Evolution is continuous with gradual changes
4.Evolution is based on natural selection
Evolution is based on 2 things (basically shows that those that have characteristics to
compete better are likely to survive and reproduce)

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1. Individuals within a population show a variety of heritable behavioural and physical
2.Capacity of environment to sustain (maintain) a population of any species is limited,
producing competition
Reproductive success- term used to describe ones ability to produce off springs
-# of workable off springs it produces in relation to the # of viable off springs
produced by other members of the same species
-Evolution bottom line is that its not physical strength but reproductive success
Natural selection is divided into 2 aspects
2. competition
Variation- the differences found in any given species in terms of the genetic biological (size,
strength, physiology) and psychological (intelligence, sociability, behaviour) characteristics
Differences between organisms genetic make-up or genotype or the physical
characteristics (phenotype)
Genotype determines how much the environment cant influence the organisms
development and behaviour (phenotype) ex: if twins were separate at birth; 1 is
better fed than their phenotypes will differ
Grants study found out that although evolution occurs over the long run, natural
selection can produce important changes in the short run.
Also phenotypic variation can produce important selective advantages that affect
Competition- outward expression of the organisms genotype- an organisms physical
characteristics and behaviour
Occurs between species when members of different species compete for similar
ecological resources like food
Dont compete for mates, however their competition for other resource indirectly
influence reproductive success because the ability to find and match up with a
suitable mate depends on the ability to defend a territory that has adequate food
Therefore, success in rearing family relies on success in competition against other
organisms of its same kind and competition against other similar organisms
(example: yellow bird competes other bird for success, but also has to compete for red
birds because they both feed off same food)
Overall, natural selection works out well- successful individuals pass on their genes
to the next generation. In the future, competition for food + other resources will only
allow the best adapted phenotypes to survive which therefore leads to evolutionary
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