Lecture 10: Interactions in Ecosystems

Question 1

Define a biological community

Answer 1

A biological community is made up of a group of populations of different species in a given area that interact

Question 2

Define interspecific interactions. Give an example

Answer 2

interactions between individuals of different species in a community
An example is competition

Question 3

Define infraspecific interactions. Give an example

Answer 3

interactions between individuals of the same species in a community

Question 4

What are the 6 kinds of interaction types? What are their effects? Are they intra- or interspecific?

Answer 4

1. Competition: -/- effects
2. Mutualism: +/+ effects.
3. Parasitism: +/- effects
4. Predation: +/- effects.
5. Commensalism: +/0 effects
6. Herbivory: +/- effects.

They are all interspecific

Question 5

What are the four kinds of defenses that have evolved in prey species?

Answer 5

1. Mechanical defense
2. Cryptic colouration
3. Chemical defense
4. Aposematic colouration

Question 6

Describe competition and provide an example

Answer 6

Members from different species compete for a resource that limits both their growth and survival and chance of reproduction (-/-).

An example is weeds growing in a garden compete with garden plants for nutrients, water, and space. Both species are being limited by the other species being there.

Question 7

Describe mutualism and provide an example

Answer 7

Both species have improved chances of survival and reproduction as a result of the presence of the other species. (+/+)

An example of this is the mycorrhizal fungi and some plants. The mycorrhizal fungi extend into the ground with their hyphae to provide the plant with nutrients and water, and in return, the plant provides the fungi with sugars and carbon. Together, they increase the other species chance of survival.

Question 8

Describe parasitism and provide an example

Answer 8

The parasitic individual improves its chances of survival and reproduction by latching onto, and feeding on, a host individual of a different species which is harmed during this interaction, reducing its chances of survival and reproduction. (+/-)

An example is ticks that feed on the external surface of their hosts.

Question 9

Describe predation and provide an example

Answer 9

One individual improves its chances of survival and reproduction by killing and consuming an individual from a different species. (+/-).

An example is a lion attacking and eating an antelope.

Question 10

Describe commensalism and provide an example

Answer 10

An interaction between two different species wherein one individual increases its chances of survival and reproduction, but the other individual has neither a reduced nor improved chance of survival and reproduction. (+/0)

An example of this is barnacles that attach themselves to whales are provided with a safe, motile place to live, transportation, and method of feeding and the whale is not harmed or helped by the presence of the barnacles.

Question 11

Describe herbivory and provide an example

Answer 11

An individual from a herbivorous (plant-eating) species consumes parts of a plant or alga to increase its chances of survival and reproduction. (+/-).

An example of this is a koala consuming eucalyptus leaves. The koala improves its chances of survival, but is harming the eucalyptus tree by feeding on it.

Question 12

Describe mechanical defenses and provide an example

Answer 12

A mechanical adaptation that allows a prey species to defend itself from predators.

An example are the spiky quills on a porcupine. These inhibit predator animals from attacking the porcupine easily.

Question 13

Describe cryptic colouration and provide an example

Answer 13

An external adaptation that allows a prey species to camouflage with its environment so as to hide from its predators.

An example is the chameleon’s ability to change its exterior colour to fit in with its surroundings.

Question 14

Describe chemical defenses and provide an example

Answer 14

A chemical adaptation that allows preys to deter predators and protect itself.

An example is the skunk’s spray.

Question 15

Describe aposematic colouration and provide an example

Answer 15

A brightly coloured exterior of an animal provides a warning signal to predators that the animal is toxic or harmful to consume.

Example is the brightly coloured poison dart frog.

Question 16

Describe Batesian mimicry and give an example

Answer 16

Batesian mimicry is a form of protection for a harmless prey species that appears like a harmful species.

An example of this the harmless king snake that has adapted the colours of the poisonous coral snake to appear as a threat to predators.

Question 17

Describe Mullerian mimicry and give an example

Answer 17

Mullerian mimicry is when two or more harmful species adapt a similar appearance so as to deter predators from the mimicking species.

An example is the similar colouration of different species of wasps.

Question 18

Describe trophic structure and trophic levels

Answer 18

The trophic structure is a way to categorize the feeding relationships between different species of an ecological community. The trophic structure is comprised of different trophic levels which are grouped species based on what they consume to gain energy and nutrition. Trophic structures represent the transfer of energy between trophic levels.

Question 19

Describe food chains and food webs and distinguish how they differ

Answer 19

Food chains are the unit within a food web that represent the transfer of energy between the trophic levels (from primary producers to decomposers).

Whereas, food webs are the diagrams that represent the connection between the different food chains that make up an ecological community.

Question 20

Approximately what percentage of the energy stored in a particular trophic level will be passed on to the next trophic level?

Answer 20

Approximately 10%

Question 21

Define keystone species and provide an example

Answer 21

A keystone species is a species that is generally not abundant in population size, but has a powerful effect on the community structure and dynamics because of their essential roles/niches.

An example of a keystone species is salmon or sea otters in the Pacific Northwest.

Question 22

What happens if a keystone species is removed from a community?

Answer 22

If a keystone species is removed from a community, the entire ecosystem will fall apart.

Question 23

What are three examples of human activities that threaten natural ecosystems?

Answer 23

1. agricultural development
2. logging and clear-cutting forests for urban development, mining and farming
3. ocean trawling

Question 24

What are the 4 different trophic levels?

Answer 24

1. primary producer
2. primary consumer
3. secondary consumer
4. tertiary consumer

Question 25

Describe primary producers and give an example

Answer 25

Primary producers are the photoautotrophic species that harness the sun’s light to create their own energy and bring energy into the food chains.

Example: photosynthetic plants and algae

Question 26

Describe primary consumers and give an example

Answer 26

Primary consumers are HERBIVORES that consume PLANTS and algae (primary producers) for energy.

Example: Koalas consume eucalyptus leaves for energy and nutrition

Question 27

Describe secondary consumers and give an example

Answer 27

Secondary consumers are CARNIVORES that consume HERBIVORES (primary consumers) for energy.

Example: dogs, cats, mice

Question 28

Describe tertiary consumers and give an example

Answer 28

Tertiary consumers are CARNIVORES that consume OTHER CARNIVORES (Secondary or tertiary) for energy.

Examples are wolves, eagles, coyotes.

Question 29

What does a pyramid of net production represent?

Answer 29

The pyramid organizes trophic levels into tiers and represents the transfer of energy within a food chain

Question 30

What are 3 major threats to biodiversity caused by humans?

Answer 30

1. habitat loss and fragmentation due to clear-cutting for agriculture or urban development
2. habitat loss and fragmentation due to dams, reservoirs, and channel modifications
3. habitat loss due to clear-cutting forests for the forestry industry