Chapter 55 Community Ecology

Question 1

What factors shape a community? Abiotic and biotic

Answer 1

Humans are part of the biotic environment and affect organisms and the energy flow and nutrient cycling throughout the environment

Question 2

What is the ultimate source of energy?

Answer 2

The sun

Energy flows from sun to earth

Question 3

A the flow of energy one way or cyclic?

Answer 3

• energy moves in 1 way/ direction

- moves from sun to producers to consumers, energy is not recycled

Question 4

Producers

Answer 4

• primary producers: autotrophic, they turn light into their own food
• plants, photosynthetic prokaryotes and protists

Question 5

Consumers

Answer 5

-get energy and nutrients (carbon) from otter organisms
-primary: herbivores who eat the producers
-secondary: carnivores who eat the herbivores
Tertiary: top predators who eat other animals

Question 6

Omnivores

Answer 6

Consumers who eat vegetation and meat, nothing goes to waste

Question 7

Detritivores and decomposes

Answer 7

Feed on organic matter and wastes/remains of other organisms
-the clean up crew

Question 8

What is a trophic level? How much energy makes it to the next level? Why is this?

Answer 8

• hierarchy of feeding relationships, energy and nutrients are transferred from one level to the next.
• Only 10% reaches the next level
• energy is lost as metabolic heat which is not useable, energy becomes stored in molecules that consumers can’t break down

Question 9

Are nutrients cyclic or one way

Answer 9

• nutrients are cycled within an ecosystem, they use a bio, chemical, geo processes
• cycles between living organism and abiotic components of ecosystems
• water cycle, phosphorus cycle, nitrogen cycle, carbon cycle

Question 10

What is a food chain?

Answer 10

• a sequence of steps where energy is captured by primary producers and is transferred to higher tropic levels
• ex: plants all the way to quaternary consumers (top carnivores)

Question 11

What is a food web?

Answer 11

• a set of food chains that are interconnected

- shows energy flow through a community

Question 12

What is bio accumulation?

Answer 12

• a chemical stored in fat that is increasingly concentrated in he tissues of animals as it moves up the food chain
• ex: a rat eats poison, predators eat that rat and also get the poison, top of the food chain eats the predator and gets the poison

Question 13

What is a tropic cascade?

Answer 13

• the interaction of a single consumer species with other species in its community
• causes progression of successive effects. Ex: a predator disappears, consumer population increases, producers have pressure from more consumers. Once you lose one species another species disappears etc

Question 14

Eutrophication

Answer 14

• lack of phosphate limits growth in aquatic producers

- reduced o2 in water and threatens survival of other species in lake

Question 15

What is the story of the gray wolf and it’s role in the Yellowstone community?

Answer 15

• wolves are top predators they really like elk
• people didn’t like them eating their farm cattle and hunters did not like that wolves were eating elk saw them as competition
• hunting led to their elimination
• since there were no more wolves, elk population exceeded the parks carrying capacity so now people had to shoot elk to bring population down
• willow population declined and so did beavers
• wolves were reintroduced after 70 years! This brought balance back to Yellowstone
• in conclusion: removing wolves caused the community to break down, when they came back it was balanced and healthy. Wolves aren’t scary bison/Buffalo are

Question 16

What is a keystone species? How important are they to a community? Is a keystone species always a predator?

Answer 16

• a species that has a large affect on the community structure, they influence them number of species in community and influences the number of trophic levels
• they are very important, if they are gone then it can lead to destruction of the community
• many of them are predators but not always. Ex: elephants, beavers

Question 17

What is an ecosystem engineer? Do they have an important role in a community?

Answer 17

• organisms that build structures for existing habitats
• they make homes for species that otherwise would not live there
• if they were removed then the species who rely on them will also disappear
• ex: elephants allow for savannas to grow and things can live there. Beavers build damns for fishes and plants to live there. Prairie dogs maintain the grasslands of North America, they loosen up soli which allows water to come in and the grass gets the water

Question 18

What is species diversity? How is species diversity determined?

Answer 18

• communities that are similar in scale differ in species, more diversity is healthy
• it is determined by species richness and evenness

Question 19

Species richness

Answer 19

-number of species present

Question 20

Species evenness

Answer 20

-relative abundance of each species. How many of each species

Question 21

What is ecological disturbance

Answer 21

Disruption in a community caused by an external force that removes species and opens up new areas for colonization

• small scale: log dislodges algae and animals attached to a rock
• large scale: hurricane, Forrest fire, tsunami, movement of a glacier, urbanization

Question 22

What are pioneer species?

Answer 22

• colonize a disturbed are

- introduced variety and they gradually replace by a succession of others

Question 23

How does primary succession differ from secondary succession? What type of disturbance preceded each? Is there life/soil left it’s the after the disturbance?

Answer 23

Primary: no existing soil or species. Lava or glacial retreat caused this. No life is left after. Hardy plants like lichens and mosses come in, soil develops from chemical weathering and erosion. Grass and shrubs move in, lichens and moss dies which contributes waste and decomposition build up. Tall trees and species come in. Takes a long time because you need to build soil

Secondary: natural disasters or human disturbance like forest clearing. The soil is left intact so there is life, which makes it easier for plants and species to come back.

Question 24

Explain the gradient found in biodiversity, what factors affect this gradient?

Answer 24

• diversity decreases with increasing latitude, moving away north or south from the equator. The tropics have the most diversity because they get the most sunlight and rainfall, less seasonal variation
• depends on weather, climate with less variation, high solar energy, seasonal change, air circulation and rainfall, landforms (windward side)

Question 25

Explain island biogeography

Answer 25

Explains the patterns of species diversity on islands. Number of species on an island represents the balance between the rate of immigration of a new species and the rate of extinction of species on the island

Question 26

The area effect

Answer 26

Relationship between size of the island and number of species. The larger the island the more species can live there

Question 27

The distance effect

Answer 27

Relationship between distance from mainland and number of species. The farther the island from mainland the fewer number of species

Question 28

Rate of immigration and extinction

Answer 28

Immigration: determined by distance. More immigration to a near island

Extinction: determined by islands size. Small islands support small population sizes. There is more extinction when the island is small since there is less socave and resources