Chapter Three Notes

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17 Dec 2010
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Chapter Three:
-Darwin came up with concept of biological evolution
-biological evolution: changes that take place in the genetic and physical
characteristics of a population or group of organisms over time
-> argued that over time, organisms originate and become adapted to their
environments by biological means
-adaptive significance: effectiveness of behaviour in aiding organisms to adapt to
changing environmental conditions
-novelty seeking: tendency to engage in behaviours that lead to new experiences
-psychologists interested in understanding both ultimate causes and proximate causes
of behaviour
-ultimate causes: events and conditions that, over successive generations, have
slowly shaped the behaviour of our species
-proximate causes: namely immediate environmental variables that affect behaviour
-Darwin then became interested in artificial selection
-artificial selection: procedure i which particular animals are deliberately mated to
produce offspring that possess especially desirable characteristics
-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 produce more
offspring than will other animals
-> Alfred Wallace proposed same idea as well
-natural selection based on 2 premises:
1) individuals within a population, show variability in heritable behavioural
and physical characteristics
2) the capacity of the environment to sustain a population of any species, is
limited; producing competition
-reproductive success: number of viable offspring an individual produces relative to
the number of viable offspring
-variation: the differences among members of a species, including physical
characteristics and behavioural characteristics
-factors responsible for variation:
1) Genotype: an organisms genetic makeup
-> differs from that of all other individuals (except for identical twins)
2) Phenotype: outward expression of a organisms genotype; an organisms
physical characteristics and behaviour
-> is produced by the interaction of individuals genotype with the
-competition: a striving or vying with others who share the same ecological niche for
food, mates, and territory
-natural selection works because the members of any species have different
-genetics: the study of the structure and functions of genes, how they are transmitted
from on generation to another, and how they operate in populations
-heredity: the sum of the traits and tendencies inherited from a persons parents and
other biological ancestors
-Gregor Mendel: uncovered basic principles of heredity by cross-breeding pea plants
-heredity determined by genetic material called DNA (deoxyribonucleic acid)
-> strands of sugar and phosphate connected by nucleotide molecules of
adenine, thymine, guanine, and cytosine
-genes: small units of DNA that direct the synthesis of proteins and enzymes
-> location of a particular sequence of nucleotides along DNA molecule
-genome: total set of genetic material of an organism
-there are no genes for behaviour, only for physical structures and physiological
processes that are related to behaviour
-genes influence us by protein synthesis
-genes also direct protein synthesis of enzymes
-enzymes: proteins that regulate structure of bodily cells and the processes occurring
within those cells
-junk DNA = non-coding DNA
-> regulate processes of other genes that synthesize proteins by genes
-> can affect evolution
-most genes are located on chromosomes
-chromosomes: threadlike structures made of DNA, found in the nucleus of every cell
-> inherit 23 individual chromosomes from each of our parents
(23 pairs = 46 individual)
-> in 22 of those pairs of chromosomes, 2 DNA molecules are of matching types
-remaining pairs of chromosomes are sex chromosomes
-sex chromosomes: chromosomes that contain the instructional code for the
development of male or female sex characteristics
-females = XX chromosomes
-males = XY chromosomes
-autosomes = non-sex chromosomes
-ova (egg) = female
-sperm = male
-sperm and ova contain only one member of each chromosome pair
-some of the genetic information on one member of a pair has been exchanged with the
information on the other member
-> produced by meiosis
-meiosis: form of cell division by which new sperm and ova are formed
-> chromosomes within the cell are randomly rearranged so that new sperm and
ova contain 23 new individual chromosomes, or half of those found in other
bodily cells
-identical twins: occurs when a fertilized ovum divides, giving rise to 2 identical
-fraternal twins: occurs when a woman produces two ova, both of which are fertilized
by different sperm
-sex is determined by the 23rd pair chromosomes; aka the sex chromosomes
-> sex of couples offspring depends on which type of sperm fertilizes the ovum
-Y-bearing produces boy; X-bearing produces girl
-alleles: alternative forms of same genes
-dominant trait: character of trait produced by heterozygous gene combinations
-recessive trait: a trait that occurs only when it is expressed by homozygous alleles
-sexual reproduction increases a species ability to adapt to environmental changes
-> leads to genetic diversity
-mutations: accidental alterations in the DNA code within a single gene
-> original source of genetic diversity
-chromosomal aberration: rearrangement of genes within chromosomes or a change
in the total number of chromosomes