#4: Animal Distribution & Ecology Flashcards
Why do similar habitats on seperate continents have different animals?
- barriers to dispersal
- Competition from established populations
- Extinction
Case of closely related species living in widely seperated areas are explained by:
1)Dispersal: one-way outward movement; active and passive
2)Vicariance: continuous habitats becomming disjunct by formation of barriers (identical to allopathy at species level)
Testable by general area cladograms of different species
Temporary LAnd bridges
“Great American Interchange”
3MYA Isthmus of Panama connected North & South America; lg interchange of mammals between 2 continents
ie raccoons, foxes, bears, tapirs deer moved south
porcupines, armadillos, opposums moved north
North America used to look alot like:
Africa
Organismal level of ecology of beavers
adaptations for living in water, eating aquatic plants/wood, anatomy, physiology, behavior
Population level of ecology of beavers
reproduce 1x/year
sensitive to drought
Community Level of ecology of beavers
beaver dams create aquatic habitat
kill trees=beaver food
change competition bet trees
Ecosystem level of ecology of beavers
beaver dams change course of water; alter carbon & nutrient cycling; an “ecosystem engineer”
Niche
Exclusive set of all environmental conditions that permit a species to survive and multiply; subject to natural selection
Depending on its niche volume an animal may be classified as:
generalist or specialist
Population growth
The Exponential curve (J-curve) occurs when there is no limit to population size.
The Logistic curve (S-curve) shows the effect of a limiting factor (in this case the carrying (K) capacity of the environment).
Niche overlap
Portion of resources shared by niches of 2 or more species
Competitive exclusion
Reduces niche overlap
Leads to specialization/character displacement
Predation
- Too efficient of a predator (one prey) can cause it’s own extinction
- If a predator relies on > one prey, both populations fluctuate
Extinction
- Speciation rates slightly > than extinction rates in evol history.
- Extinction rates show peaks/valleys
- Species with > geographic ranges have
Rate of Extinction related to human:
- destruction of habitats, climate change
- over-fishing and poaching
- illegal trade in exotic pets
- spread of exotic species
Why we should care about biodiversity loss:
plants produce O2
pollination by bees saves $19Billion
Medicines
Factors responsible for loss of biodiversity
- greenhouse gas emissions; climate change
- ozone depleting chemicals-hole in ozone layer
- Air pollutants: human health, acid rain
- pesticides, fertilizers, medical waste: human health, animal populations, eutrophication of freshwater
- exotic species: conversion of habitat, human health
- habitat loss: loss of biodiversity
Carrying capacity of earth
animals kept below or at carrying capacity by disease, famine, predation or weather
Human population is growing because
tech and medical advances have eliminated many of the above factors
Limits to carry capacity of earty
1/3 of 2Bill people alive today are malnourished
Examples of lessons learned
- Removal of coyotes (keystone predator) in TX to protect livestock, doubled rodent populations causing greater economic loss to stored grains
- extinction of Hawaiian birds has caused extinction of native plants due to no longer being pollinated
