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Lecture 3

BIO120H1 Lecture Notes - Lecture 3: Beltian Body, Island, Sexual Dimorphism


Department
Biology
Course Code
BIO120H1
Professor
Spencer Barrett
Lecture
3

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BIO 120 Lecture 3 Notes
Charles Darwin’s voyage on HMS Beagle (1831-1836)
Age 22, ship’s naturalist
Most time spent in South America
Propose of the voyage is to make the map for ships
Observations of fossils, geographical distribution of plants and
animals, and /ora and fauna of oceanic islands
Tropical forests in Brazil
Very high species diversity of plant and animal groups compared
with temperate zone
Many more biotic interactions between organisms, especially
coevolved mutualisms between plants and animals
Year round warmth results in rapid growth of insect and microbial
populations.
Pest and disease pressures on plants more intense.
Distance between individuals of each tree species are quite
considerable. Distance between each species can be quite
extreme
Tropical trees are largely animal pollinated whereas temperate trees
are mostly wind pollinated
Tropical forests have high species diversity and individuals of the
same species are widely separated (unlike temperate forests)
Tropical forests are also largely evergreen (non-deciduous)
Dense canopies and long-distances between trees make wind a
poor agent of pollen dispersal, (wind pollination is very
ine7ective because canopies stop the process of pollination), so
animals are more e7ective pollinators
Bees, butter/ies, months, birds and bats pollinate most tropical
trees, (they travel long distances) while most temperate trees
are wind pollinated
Euglossine bees as long distance pollinators of tropical plants
Tropical ecologist Daniel Janzen has made several major
contributions to our understanding of tropical forest plant insect
interactions
Used mark-recapture techniques to demonstrate that large bees
travel up to 23 km during a day
Today widely recognized that bees, moths and hummingbirds
travel long distances during “trap line” (have a lot of iron fences)
foraging
Janzen’s pest pressure hypothesis: predicts that tropical tree
seedlings are less likely to establish close to the maternal
(mother side) parent
Seedlings are most dense close to the parent tree
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