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Summary Genetics, Ecology And Evolution (WBBY005-05)
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Genetics, Ecology & EvolutionBeukeboom lec. 1 Biology Ch. 21 How evolution works
Lamarck’s two principles:
Use and disuse: parts of the body that are used extensively become larger and stronger,
while those that are not used deteriorate.
Inheritance of acquired characteristics: an organism could pass modifications like a giraffe
stretching its neck to reach leaves, to its offspring. The long, muscular neck of a giraffe had
evolved over many generations as giraffes stretched their necks even higher.
Genetic variation → natural selection → adaptation → evolution
Genetic variation: e.g. mendelian genetics, quantitative genetics, population genetics.
Natural selection: individuals with certain heritable traits leave more offspring than others.
Adaptation: the ability of an organism to survive and reproduce in specific environments.
Evolution: a change over time in the genetic composition of a population.
Blending inheritance: mixing of traits of both parents. Red flower and white flower → gets pink
flower.
Particulate inheritance: traits inherit via discrete units. Red flower and white flower → gets or a
white flower, or a red flower.
Paleontology: study of fossil.
Catastrophism: evolution occurs through sudden leaps (Cuvier).
Gradualism: change takes place through slow but continuous processes (Hutton).
Uniformitarianism: same geological processes are acting today as in the past (Lyell).
Artificial selection: breeding of individuals with desired traits by humans (e.g. wild mustard).
3 requisites of adaptation by natural selection:
Variation in reproductive success (different numbers of offspring).
Genetic basis for variation.
Correlation between variation in trait and reproductive success.
Homology: identity of a trait in two or more species by descent form a common ancestor.
Morphological homologies (e.g. arm of a human/cat, wing of a bat, fin of a whale).
Developmental homologies (e.g. foetus of a fish/reptile/bird/human).
Molecular homologies: all species share the same genetic code, but DNA sequences change
over time. Rhesus monkeys have 95% of the same DNA as humans have.
Biogeography: study of geographical distribution of organisms and its underlying causes.
Endemic species: are only found at one place in the world (islands).
Evolutionary medicine: natural responses to diseases are the product of selection and evolution, and
can act as guide to medical treatment.
Evolutionary psychology: human mind is the product of the environment in which humans have
evolved, which can help to understand human behaviour.
,Convergent evolution: independent evolution of an organism in different ecosystems which has the
same outcome (squirrel).
Analogous features: share similar function, but not common ancestry.
Homologous features: share common ancestry, but not necessarily similar function.
Vestigial organs: of a human it is the tailbone, appendix and wisdom teeth.
Chapter 25 Macroevolution
Plate tectonics: the theory that the continents we live on move over time and forms every +/- 300
million years a supercontinent.
Consequences of continental drift:
It alters the habitats in which organisms live. E.g. the formation of Pangaea greatly altered
the physical environment and climate, which drove some species to extinction and provided
new opportunities for groups of organisms that survived the crisis.
It also promotes allopatric speciation on a grand scale. When supercontinents break apart,
regions that once were connected become isolated.
It can help explain puzzles about the geographic distribution of extinct organisms. E.g. why
fossils of the same species of an organism have been discovered in both Brazil and Ghana.
Adaptive radiations: periods of evolutionary change in which groups of organisms form many new
species whose adaptations allow them to fill different ecological roles, or niches, in their
communities. This increases the diversity of life.
This occurred especially after each of the big five mass extinctions, when survivors became adapted
to the many released ecological niches.
Heterochrony: an evolutionary change in the rate or timing of developmental events. E.g. an
organism’s shape depends in part on the relative growth rates of different body parts during
development. Changes to these rates can alter the adult form substantially, as seen in the contrasting
shapes of human and chimpanzee skulls.
Paedomorphosis: when a species retains body features that were juvenile structures in an ancestral
species (e.g. larves).
Homeotic genes: master regulatory genes that determine such basic features as where a pair of
wings and legs will develop on a bird.
Beukeboom lec. 2 Biology Ch. 14 Mendelian Genetics
, Genetics: study of heredity and hereditary variation.
Gene: unit of hereditary information, nucleotide sequence in DNA (or RNA in some viruses).
Allele: alternative version of a gene (that may produce distinguishable phenotypic effects).
Dominant: trait is fully expressed in heterozygote.
Recessive: trait is not expressed in heterozygote.
Diploid: two sets of chromosomes (or copies of a gene).
Haploid: one set of chromosomes (or one copy of a gene).
Homozygote (homozygous): two identical alleles of a gene.
Heterozygote (heterozygous: two different alleles of a gene.
Genotype: ‘genetic make-up’, sum of heritable factors.
Phenotype: ‘appearance’, sum of heritable- and environmental factors.
Mendel’s first law: PRINCIPLE OF SEGREGATION
The two alleles for a heritable character segregate (separate from each other) during gamete
formation and end up in different gametes. Thus, an egg or a sperm gets only one of the two
alleles that are present in the somatic cells of the organism making the gamete.
Mendel’s second law: PRINCIPLE OF INDEPENDENT ASSORTMENT
Alleles of different genes split independently resulting in a 9:3:3:1 ratio in the F 2-generation
of a dihybrid cross.
Difference between hypothesis of
dependent and independent
assortments:
Monohybrids: true-breeding parents
that are heterozygous for the one particular character being followed in the cross (Yy).
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