16 Flashcards
(21 cards)
Why can energy pyramids never be top-heavy?
because energy is always lost when moving up trophic levels.
What are herbivore abundance primarily limited by?
plant quality and quantity.
Tropic cascades are always topdown/bottom up effects?
Indirect Topdown effects
Trophic cascades are more abundance in aquatic/terrestrial ecosystems?
Aquatic
!Keystone species?
Strong effects because of their role in a community (a removal of a keystone species causes a trophic cascade)
!Foundation species?
Species contributing most of the spatial structure of the community, the competitive dominants.
!!!Are bottom up effects always negative/positive in energy passing?
positive
Primary producers benefit when there is an odd/even number of trophic levels?
Odd
Ratios of plant log (plant biomass with pred:plant biomass without pred) and herbivore log (herbivore biomass with pred:herbivore biomass without pred) that cause the strongest trophic cascades?
Plant log ratio»_space; 0 & herbivore log ratio «_space;0
Terrestrial?
poor plant quality means that releasing herbivores from predation will have little impact on plant biomass.
Why are aquatic systems have strong and more variable trophic cascades?
herbivory rates are much higher and have higher quality plants, which allow for efficient depression of plant populations.
Biodiversity rises/declines with habitat fragmentation?
Declines
Edge effects?
Contribute to local extinctions since edge habitats can often be more exposed to abiotic and biotic factors that can limit growth.
Why is decreasing diversity non-benefiting to humans? 4•
*Ethical and aesthetic concerns
*Loss of ecosystem services that sustain human health and well being, such as food and medicines.
*About 80% of our diet and 25% of pharmaceuticals originated in tropical plants
*traditional uses of tropical forests result in 4-5x more economic benefit compared to unsustainable forest harvesting.
Types of habitat changes? 3*
*Habitat loss: conversion of ecosystem to another use
*Habitat degradation: changes that reduce quality of habitat for many, but not all species.
*Habitat fragmentation: breaking up of continuous habitat into habitat patches amid a human-dominanted landscape.
Extinction debt?
when it takes a long time for species to go extinct after habitat loss/fragmentation.
How to measure extinction debt?
Use historically damaged habitat to predict which species will eventually go extinct in recent damaged habitat.
What has been causing most extinctions to date? 5•
*Habitat changes
*over harvesting
*pollution (including N deposition)
*invasive species
*climate change
!!!Pros of single large reserve? 4*
Why exactly better at supporting top predators?
*Reduces edge effects
*Better at supporting top predators
*Supports larger populations
*Allows connectivity between protected individuals
SLOSS?
(Single large or several small reserves.
Pros of several small reserves? 3*
*can protect more types of habitat
*May better protect rare or endemic species
*Prevents disease from spreading.
