Gause's principle of competitive exclusion - no two species can occupy identical niches indefinitely when resources are limiting -either they can't exist for a long time or there niches are somewhat different
Sympatric species often avoid competition by living in different portions of the habitat,...
Bio 250 Exam 3 Practice Questions and
Answers
Gause's principle of competitive exclusion ✅- no two species can occupy identical
niches indefinitely when resources are limiting
-either they can't exist for a long time or there niches are somewhat different
Sympatric ✅species often avoid competition by living in different portions of the
habitat, or using different food or other resources
Ex: anolis lizards on caribbean island
Character displacement ✅differences between symmetric species that are favored by
natural selection in order to partition resources and reduce competition
Ex: Darwin's finches
Reproductive character displacement ✅species recognition and mate choice using
wing pigmentation in damselflies
Predation ✅one organism consuming another, kills prey pretty much immediately
Sea otters ✅-predators to sea urchin
-almost total removal of sea otters from CA during 1800s
-led to increase in red urchins
-and decrease of kelp beds
Predation and coevolution ✅-predation is strong selection pressure on prey
populations, so the prey may evolve traits to avoid capture
-natural selection favors traits in the predators to overcome the prey adaptations
-coevolution & arms race
-can also happen with herbivores and plants, parasites and hosts
Chemical defenses ✅-secondary chemical compounds that are toxic or disrupt
development
-ex: mustard oil in Brassicaceae and cabbage white butterflies
Mechanical barriers to herbivory ✅trichomes, glandular exudates, latex and egg
mimics
Passionflower plants and heliconius butterflies ✅-lay their eggs on passion vines and
caterpillars eat the leaves
-the butterflies search visually for the plants, so intense selection pressure on
appearance
, Egg mimics ✅_______ ___________ reduce the amount of oviposition because adults
avoid larval competition (cannibalism and egg predation)
Secondary compounds ✅animals can use _______________ ______________ of
plants for their own protections
Monarch butterflies and milkweed ✅-monarch butterfly caterpillars can feed on toxic
milk weed and store up cardiac glycosides in fat to protect themselves from predators
Eating plant toxins ✅-cinnabar moth and african variegated grasshopper
-get toxins called pyrrolizidone alkaloids (from ragwort)
-both species evolved enzyme that allows them to store the toxin for self defense
Chemical defenses of animals ✅poison dart frogs produce toxic alkaloids in mucus,
distasteful and deadly to animals to try and eat
Defensive coloration ✅-aposematic
- showy coloration is characteristic of animals that use poison and stings to repel
predators
Batesian mimicry ✅-henry bates
-non poisonous species that resemble protected species
-mostly in butterflies and moths
-eastern coral snake, scarlet king snake
Mullerian mimicry ✅-fritz mueller
-several unrelated but protected species to to resemble one another
-predator learns more quickly to avoid them
-can evolve innate avoidance
Mutualism ✅-both species benefit
-beneficial association between 2 species
Parasitism ✅one benefits and the other is harmed
Commensalism ✅one benefits and the other isn't harmed or benefited
Obligate mutualism ✅-necessary association
-one organism cannot survive without the other
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