Chapter Three – Evolution, Heredity, and Behaviour
Part 1: The Development of Evolutionary Theory (58)
-Charles Darwin argued that, over time, organisms originate and become adapted to their
environments by biological means – theory of evolution.
-His concept of biological evolution – changes that take place in the genetic and physical
characteristics ofa population or group of organisms over time – is now the primary explanation
of the origin of life.
-His theory transcends biology and has influenced other fields such as psychology.
-In psychology, Darwin’s concept of evolution gave psychologists a new way to understand
behaviour. Psychologists could look at behaviour in terms of origins and adaptive significance
–the effectiveness of behaviour in aiding organisms to adapt to changing environmental
-A complete understanding of any behaviour requires that we understand both the past and the
present conditions that influence it.
-When trying to figure out which behaviour is more beneficial, we must ask ourselves:
1) What events and conditions in a person’s lifetime might contribute to a tendency to seek or to
avoid the specific behaviour (ex. Novelty); what function does the behaviour (ex. Novelty
seeking) or its converse serve in helping people adapt to the changing circumstances of life?
2) What events and condition in the evolution of our species favoured or punished people that
exhibited this behaviour (ex. Novelty seekers); what functions has the behaviour (ex. Novelty
seeking) served in the history of human kind?
-Psychologists might research how the past environmental conditions favoured novelty seeking
over more conservative reactions and how the immediate environment influences day-to-day
-They are interested in understanding both ultimate causesof behaviour –evolutionary
conditions that have slowly shaped the behaviour of a species over generations – and
proximate causes, immediate environmental events and conditions that affect behaviour.
-By understanding how adaptive behaviour developed through the long-term process of
evolution, psychologists are able to gain a more thorough understanding of our ability to adjust
to changes in our immediate environment.
-Considering the role of evolutionary factors in behaviour has resulted in a new subfield within
psychology known as evolutionary psychology, in which psychologists investigate how an
organism’s evolutionary history contribute to the development of behaviour patterns and
cognitive strategies related to reproduction and survival during its lifetime.
-The study of evolutionary psychology may help us understand the ongoing evolution of culture
–the sum of socially transmitted knowledge, customs, and behaviour patterns common to a
particular group of people.
The Voyage of the Beagle (59)
-1831, Darwin (from England) and Captain Robert Fitz Roy set a sail on the HMS Beagle for a
five year long voyage to explore the coast of South Africa, South America, South Atlantic, and
Indian oceans and most famously the Galapagos Islands off the coast of South America.
-Plato’s doctrine of essentialism stated that all living things belong to a fixed class or kind,
defined by an essence that characterizes it alone ÆA book which Darwin had read.
-Upon his return, he became interested in natural selection –a procedure in which particular
animals are deliberately mated to product offspring that possess especially desirable
characteristics. He looked at this practise in pigeons and bred pigeons himself for a while.
-He wondered if it was possible to produce such different varieties of pigeons that it would
result in a new species.
-He was struck by the idea of natural selection –the consequence of the fact that, because
there are physical and behavioural differences among organisms, they reproduce differentially,
Within a given population, some animals – the survivors – will product more offspring than will
-He came to this realization in 1838 but did not publish his findings until 20 years later.
Natural Selection (61)
-The ability of an individual to produce offspring defines that individual’s reproductive
success –the number of viable offspring an individual produces relative to the number of viable
offspring produced by other members of the same species.
-The two aspects of natural selection, variation and competition, are the critical factors that
determine whether any animals will be reproductively successful.
-Variation refers to the differences among members of a species, including physical
characteristics such as size, strength, or physiology, and behavioural characteristics such as
intelligence or sociability.
-What factors are responsible for these sorts of variations? Genotype and phenotype.
-An individual organism’s genetic makeup, or its genotype, differs from that of all other
individuals (except for twins). As a result of these genetic differences, an individual organism’s
physical characteristics and behaviour, or its phenotype, also vary from every other individual.
-Every individual’s phenotype is produced is produced by the interaction of its genotype with
-Although evolution occurs over the long run, natural selection can produce important changes
in the short run – in the space of only a few years.
-Phenotypic diversity is very important for a species survival because it ensures that if an
unexpected natural disaster occurs, the species will not go extinct.
-Competition is a striving or competing with others who share the same ecological niche for
food, mates, and territory.
-Competition can be for mates, territory, food and all factors affect the animal’s success.
-Over time, competition for food and other resources will allow only the best-adapted
phenotypes to survive, thereby producing evolutionary change.
-These changes can be measured using techniques based on correlational methods.
Part 2: Heredity and Genetics
-Genetics is the study of the genetic makeup of organisms and how it influences their physical
and behavioural characteristics.
-Closely related to genetics is heredity –the sum of the traits and tendencies inherited from a
person’s parents and other biological ancestors.
-Following Darwin’s The Origin of Species, Mendel uncovered the basic principles of heredity.