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Lecture #4 Notes

Course Code
Maria Arts

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Lecture #4
-life history: is an organisms lifetime pattern of growth, development, and reproduction
involves adaptations ( physiological, morphological, adaptations to environment etc)
-an organisms decisions are going to be a balance between the costs and benefits
Slide 4:
-as soon as you put energy into one aspect, then it comes at a cost of putting energy into
e.g. putting energy into reproduction, cost is growth ( they are smaller) - why males are
usually bigger
Slide 5:
-sexual reproduction: fusion of haploid egg and sperm to form diploid zygote
major source of genetic variation due to the recombination of chromosomes during
gamete production
-asexual reproduction produces offspring without fusion of egg and gamete
Slide 6:
- modes of asexual reproduction
rhizomes: strawberry plants
splitting in two : paramecium
budding: hydra
parthenogenesis: aphids
-organisms that rely on heavily on asexual reproduction can revert to sexual reproduction
usually due to environmental change
e.g. hydra- sexual reprod
pg. 2
Slide 1:
Asexual reproduction:
low genetic variability in the population
maybe unable to adapt to a change in environmental conditions
-benefits have to outweigh the costs
Slide 2:
Sexual Reproduction:
parents only contribute one half of their genes
specialized reproductive organs
energetically expensive

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expense of reproduction not equally shared between parents
-hermaphroditic: organisms possess both male and female organs
Slide 5:
genetic variability
pg. 3
Slide 2:
-Parents cooperate to raise young
Increased survival of young and parents’ genes
-But…one of the parents may cheat
To increase fitness by producing more offspring
-Polygamy…. Two or more mates ( pair bonds exist)
Individual having multiple mates is generally not involved in caring for young
Slide 4:
-Sexual selection is a subset of natural selection
-Sexual dimorphism: two sexes differ in body size, ornamentation, and color
Slide 5:
-Intrasexual selection involves male to male competition
Large size, aggressiveness, antlers, horns
Pg. 4
Slide 1:
-What does tail size imply about the individual :
-Secondary…. Superiority
in choosing a mate with large tail feathers ( bright plumage), a female is choosing
the most fit
Slide 2: Female Choice
-The driving force…. Selection by females
-Proposed hypothesis: health vs. disease
- Male investment is elaborate …. E.g. foraging, defense
-Green sword tail ; some of them have really long swords
Slide 4:
-Females preferred males with longer swords ( conclude that long swords enhance
mating success increase in reproduction, & increase in fitness)
Slide 5:
-As the sword length increases, the time spent increases
Slide 6:
-In some cases, researchers experimented by shortening the sword
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