Ecology Test 3

Predator adaptations to be more efficient at capturing/eating prey

Predator adaptations to be more efficient at capturing/eating prey

• strong jaws to crush through bone

• chew up and down instead of side-to-side

• eyes on the front of their head, allowing depth and distance perception

Physical Adaptations to escape being eaten

• large size

• body armor

• tough leaves

• spines and thorns

• hairs that can pierce skin

cryptic coloration

• prey is camouflaged or resembles its background

  • ex.) polar bears in the snow

warning coloration (aposematic)

• Animals that warn predators of their dangerous nature

• predators learn not to eat organisms that have distinct coloration or toxins

  • ex.) the rattle of a rattlesnake

  • ex.) the bright colors of a poison dart frog

mimicry

• the prey resembles another organism that is toxic or very fierce

  • ex.) Monarch and Viceroy

Predation

Individuals of one species (predators) feed on, and directly harm, individuals of another species (prey).

• can be plants or animals

Carnivory

Prey

• mobile (alive and running away)

• killed

• higher nutrient content (have to eat less)

Predator

• broad diets

Herbivory

Prey

• non-mobile (stationary plants)

• varying levels of harm (eating the leaves or top of grass doesn’t kill the plant)

• lower nutrient content (have to eat more)

Predators

• narrow diets

  • ex.) pandas and bamboo

Know the meaning behind an “evolutionary arms race”.

• a struggle between competing sets of co-evolving genes

  • physical and behavioral traits that develop escalating adaptations and counter-adaptations against each other

• may occur between individuals of the same species or between species

• affects both predator and prey

• explains some of the unusual traits that have evolved

“evolutionary arms race” example

rattlesnake vs. ground squirrel

• over time, the rattlesnake’s venom has become more potent but the ground squirrel, whose only enemy is the rattlesnake, has developed stronger and stronger immunity to its venom

Lotka-Volterra model assumptions

1. only two species exist: fox and rabbit

2. rabbits are born and then die through predation or eventual death

3. foxes are born and their birth rate is positively affected by the rate of predation, and they die naturally.

Be able to draw a state-space graph and predict the short-term trend in prey and predator populations (given an initial starting point, provided by me).

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Know why it is hard to replicate oscillations we see in nature, in the lab.

it’s hard to replicate what happens in the wild in a lab because you can’t account for all the variables

Know the factors in the model that control the amplitude and period of predator/prey oscillations (you won’t need to calculate anything here).

• amplitude

  • is determined by the initial population size.

• period

  • is based on the prey growth rate and the predator death rate

Understand the assumptions of the predator-prey Lotka-Volterra models.

• growth of prey is only limited by predation

• predator is a specialist

• Predators can consume an infinite number of prey

• Predator and prey encounter one another randomly in a homogenous environment

biodiversity

• the variety of life on Earth, in all its forms

  • ex.) from genes and bacteria to entire ecosystems like forests or coral reefs

• The degree of diversity found within a specific ecological system

species diversity

• made up of species evenness and species richness

• Diversity is greatest when all the species present are equally abundant in the area

• affecting factors

  • latitude (terrestrial)

  • area and isolation of habitats

  • environmental complexity

  • disturbance

  • human stressors

biodiversity vs species diversity

Biodiversity includes species diversity, genetic diversity, and ecosystem diversity

Species Evenness

• the number of species individuals in an environment

Species Richness

• the number of different species in a given area.

• considerations

  • Number of samples taken

  • Time devoted to sampling

  • Representation of habitats

Know how to calculate the Shannon Diversity Index

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Species Accumulation Curve

• a graph that counts species, not individuals of a species

• counts species richness

Species Rank Curve

• counts the individual number of a species

• counts species evenness

Direct Interactions

• competition, predation, etc., between two species

• does not involve intermediary species

Indirect Interactions

• the effects of one species on another through a third species

• types

  • exploitative competition

  • apparent competition

  • trophic cascades

  • trophic facilitation

Exploitative Competition

Two species share a common resource and affect each other indirectly through the resource

Apparent Competition

• Two species share a common predator

• The two prey species have negative effects on each other, even though they feed on different resources

Trophic Cascades

• Predators reduce mortality on the food of their prey by reducing prey density

• In a food web, changes in populations of consumers at higher trophic levels may indirectly affect trophic levels below them.

• negative interaction

Trophic Facilitation

• when a consumer is indirectly helped by a positive interaction between its prey and another species

keystone species

A species other species in an ecosystem largely depend on. If it were removed, the ecosystem would change drastically.

• ex.) wolves

ecosystem engineers

• Any species that creates, significantly modifies, maintains, or destroys a habitat.

• These organisms can have a large impact on species richness and landscape-level heterogeneity of an area.

  • ex.) beavers

foundational species

• Foundation species are considered the “base” of a community, having the greatest influence on its overall structure.

• They are usually the primary producers—organisms that bring most of the energy into the community.

Primary Succession

• when plants and animals first colonize a barren, lifeless habitat.

  • ex.) when lava cools and creates new rocks

Secondary Succession

• Species in an area have been removed, but seed and spores remain.

  • ex.) forest fire

Primary + Secondary Spectrum of Disturbance

• primary succession must have a rare, high-intensity event to occur

• secondary succession must have an infrequent, medium-intensity event to occur

How can you study succession over long periods of time without spending that long studying in the field?

Cowles: Space for Time Substitution

• a method for studying slow ecological processes at sites that are at different stages of development

Clement’s hypothesis about how succession proceeds

• after a disturbance, any ecosystem would eventually return to its original assemblage of species

• predictable model

  • A superorganism that "arises, grows, matures, and dies... is comparable in its chief features to the life history of an individual plant.”

Gleason’s hypothesis about how succession proceeds

• the idea that vegetation in communities changes over time in response to disturbance.

• succession is viewed as the response of species to environmental conditions to maturation and fluctuation

• ”individualist” model

  • individual species independently respond to environmental conditions

Elton’s hypothesis about how succession proceeds

He emphasized that the only way to predict the trajectory of succession was to understand the biological and environmental context in which it occurred