Ecology and Communities

Question 1

What is a community?

Answer 1

A community is a group of populations of different species living in a close proximity, thus they can interact

Question 2

What is a niche?

Answer 2

A niche is the sum total of an organism’s interaction with biotic and abiotic resources of it’s environment.

Question 3

What is the difference between a fundamental niche and a realized niche?

Answer 3

A fundamental niche:

• The theoretical niche where no limiting factors are present.
• No competitors, no disease, no parasites, no predators

A realized niche:

• The niche that is actually organized by the organism
• For example, if a predator is present, the organism will no longer feed in that area.
• Thus differs from the fundamental niche

NB for the DAT

Question 4

What is symbiosis?

Answer 4

Symbiosis is the ecological relationship between different species of organisms living in the same community
- Can be harmful, beneficial, or neutral

Question 5

What is mutualism?

Answer 5

Mutualism is a symbiotic relationship where both organisms benefit

• Bacteria make vitamin K while living in the human intestine
• Pollinators and flowering plants
• yucca moth and yucca plant

Question 6

What is commensalism?

Answer 6

Commensalism is a symbiotic relationship where one organism benefits and the other organism is neither harmed nor helped.

• Bird using a tree as a nesting site (tree gets nothing in return, but is not harmed)
• A plant like a fern uses another for shade
• Barnacles living on a whale. Doesn’t harm the whale, but barnacles get benefit of constant water filtration for food.

Question 7

What is parasitism?

Answer 7

Parasitism is a symbiotic relationship where on organism benefits, while the other organism is harmed.

• Blood fluke infects a human and causes enlargement of the liver and spleen in addition to other disorders
• Athletes foot fungus

Question 8

What is interspecific competition?

Answer 8

Interspecific competition is when individuals of different species compete for a resource that they depend on for their growth and survival. (Fox and lynx compete with each other for prey). There are two types:

• Interference competition: Kill competitors or chase them away from a resource.
• Exploitation competition: Use up a resource before anything else can

Question 9

What is interference competition?

Answer 9

Interference competition is a type of interspecific competition where competitors kill or chase each other away from a resource

Question 10

What is exploitation competition?

Answer 10

Exploitation competition is a type of interspecific competition where competitors attempt to use all of a resource before the other organism does.
- Both have equal access, but one uses it at a faster rate

Question 11

What is competitive exclusion?

Answer 11

Competitive exclusion occurs when two or more species are fighting over the same resource.

• Both species can’t coexist
• One will have a slight advantage that will cause the other one to be eliminated
• If niches of species are the same, two species will be unable to coexist permanently in a community

Question 12

What is resource partitioning?

Answer 12

Resource partitioning occurs when organisms in the same niche branch out to form different niches for survival. Examples:

• Three plants living in the same field exploit a different part of the soil. Each is able to survive, hence they coexist
• Three types of lizards, live in close proximity and have competition of resources. One likes the sun, one likes the shade, and one likes high places. There is a possibility that all three could survive, given they stay in the areas only they like.
• The fundamental niche is different than their realized niche.

Question 13

What is predation?

Answer 13

Predation is when an organism gets its nutrients from killing and consuming another organism

• When predators can prevent their prey from overshooting its carrying capacity, then a stable coexistence can occur.
• It is often the most important factor that determines population size. It is regarded as a powerful agent of natural selection
• Predators help in population control

Question 14

What is a parasite?

Answer 14

A parasite obtains food from the host, which it might kill, or might not.

• The parasite will live in or on the host for a long time
• Parasitism could be considered a form of predation

Question 15

What are the characteristics of a predator?

Answer 15

Natural selection favors the most efficient predator. Many predators have the following:

• Acute senses
• Teeth or fangs
• Stingers
• Claws
• Fast to move
• Agile
• Thick and strong structures like beaks and bills

Question 16

What are some defensive adaptations seen by prey animals?

Answer 16

Prey animals can exhibit the following adaptations:

• Morphological features
• Chemicals
• Concealment and camouflage
• Aposematic signals
• Mimicry

Question 17

What are the morphological features that are exhibited by prey?

Answer 17

Morphological features exhibited by prey can help them avoid predation. They include:

• Pill bugs and armadillos rolling into a ball
• Porcupine spikes
• Lizards breaking off their tail
• Hermit crabs carry sea anemones on their back

Question 18

How do prey animals use chemicals to fend off predators?

Answer 18

Prey animals use chemicals to fend off predators in the following ways:

• Plants fend off predators with toxins including: Nicotine, caffeine, morphine, cocaine, strychnine, and quinine. These alkaloids have pharmacological effects on bothe humans and animals
• Some alkaloids inactivate enzymes, others disrupt DNA repair mechanisms.

Question 19

What are aposematic signals?

Answer 19

Aposematic signals are signals to predators that an organism is poisonous.

• Aposematic coloration: Many unpalatable or poisonous organisms display bright colors
• Skunks striped tails, colorful frogs and insects, etc

Question 20

What is mimicry?

Answer 20

Mimicry is when a species has the same or similar appearance as another. There are two types

• Batesian mimicry: Deception
• Mullerian mimicry: Part of the cool poisonous gang with gang colors to match

Question 21

What is Batesian mimicry?

Answer 21

Batesian mimicry is where we see deception.

• A harmless organism “pretends” it’s dangerous by looking like an organism that is poisonous and dangerous
• A harmless fly resembles a hornet

Question 22

What is Mullerian mimicry?

Answer 22

Mullerian mimicry is where we see similar types of poisonous or dangerous organisms with the same or similar appearance.
- Ex: Bees and hornets with black and yellow striping

Question 23

What is species diversity?

Answer 23

Species diversity refers to the variety of organisms which are different that make up the community and includes:

• richness: number of different species
• evenness: the relative species abundance

The more species you have and the more evenly distributed they are, the greater the species diversity

Question 24

What is a food chain?

Answer 24

A food chain is the sequence of organisms in which energy moves

• Contains a primary producer: ex: grass
• Contains a primary consumer: grasshopper
• Contains a secondary consumer: rat
• Contains a tertiary consumer: snake
• Contains a quaternary consumer: hawk
• And so on, until the apex predator is shown

Question 25

What is a food web?

Answer 25

A food web is multiple connected food chains

Question 26

What are detritivores?

Answer 26

Detritivores are organisms such as soil arthropods and earthworms that ingest the detritus (dead plant and animal tissue)

Question 27

What are decomposers?

Answer 27

Decomposers such as bacteria and fungi obtain their energy through breaking down dead organic matter.
- Usually decomposers are not included in any food chain diagram

Question 28

What is an ecological pyramid?

Answer 28

An ecological pyramid:

• Shows the trophic levels of a community
• Producers have the most energy and the most number of individuals
• As you go up the pyramid these trends decrease
• Different trophic levels represent different amounts of potential energy.
• The producers have the greatest level of potential energy, and it decreases at each level all the way up to the apex predator

Question 29

What is a biomass pyramid?

Answer 29

A biomass pyramid shows the abundance of biomass for each trophic level in a food chain.

• At the bottom you would have grasses and at the very top the apex predators.
• You generally divide by ten between each level

Question 30

What is a keystone species?

Answer 30

A keystone species is a species that keeps the ecosystem from collapsing. Examples:

• A sea otter kills off many sea urchins that do damage to kelp forests. Without sea otters, sea urchins would destroy them
• A jaguar kills many prey animals that would decimate the plant population if their numbers weren’t kept in check.