Ecology Chapter on Species Interactions

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Questions and Answers

What does species richness measure in a community?

The variety of different species present

The total biomass of the community

The total number of different species (correct)

The proportion each species represents of the total individuals

How does relative abundance contribute to species diversity?

It measures the total biomass of the community

It indicates the variety of different species present

It only considers the total number of individuals

It shows the frequency of each species in relation to others (correct)

Which scenario best describes a community with high species diversity?

Only a few species are present in high abundance

Many species are present but all have low populations

All species have similar population sizes (correct)

One or two species are highly abundant while others are rare

What is the impact of interspecific competition on species interactions?

It is detrimental to one or both species Signup and view all the answers

Which of the following statements regarding species abundance is true?

Two communities can have the same species richness but different relative abundances Signup and view all the answers

What defines an ectoparasite?

A parasite that feeds on the external surface of the host Signup and view all the answers

In mutualism, which of the following statements is true?

Both species benefit from the interaction. Signup and view all the answers

Which type of mutualism requires one species to survive?

Obligate mutualism Signup and view all the answers

What is an example of commensalism?

Clownfishes living among sea anemones Signup and view all the answers

Which of the following describes both endoparasites and ectoparasites?

They benefit by harming their hosts. Signup and view all the answers

What occurs when two species compete for the same limited resource?

Competitive exclusion Signup and view all the answers

What defines the fundamental niche of an organism?

The potential ecological niche in the absence of competition Signup and view all the answers

What is a likely outcome when two species with identical niches compete for resources?

Resource partitioning Signup and view all the answers

What describes the realized niche of an organism?

The niche actually occupied in the presence of competition Signup and view all the answers

Which of the following is NOT an example of interspecific interaction?

Intraspecific competition Signup and view all the answers

Which principle states that two species competing for the same limiting resources cannot coexist in the same place?

Gause's Law Signup and view all the answers

What often leads to resource partitioning between species?

Natural selection modifying resource use Signup and view all the answers

What is the effect of strong interspecific competition?

Competitive exclusion of one species Signup and view all the answers

What defines a dominant species in an ecosystem?

Species that have the highest biomass or abundance Signup and view all the answers

How does primary production impact the energy budget of an ecosystem?

It defines the total energy available for all organisms Signup and view all the answers

What is a key characteristic of invasive species?

They often lack predators or diseases in the new environment Signup and view all the answers

Which of the following concepts best describes the interconnected nature of food chains?

Food web Signup and view all the answers

What role do keystone species play in an ecosystem?

They exert a disproportionately large impact on their environment Signup and view all the answers

What is character displacement primarily concerned with?

The tendency for characteristics to become more divergent in sympatric populations Signup and view all the answers

Which of the following is NOT a feeding adaptation of predators?

Camouflage Signup and view all the answers

What adaptation might a prey animal use to signal danger to others?

Alarm calls Signup and view all the answers

In Batesian mimicry, which statement is true?

A palatable species mimics an unpalatable or harmful model Signup and view all the answers

What type of relationship does herbivory refer to?

A herbivore eating parts of a plant Signup and view all the answers

Which of the following is a type of symbiotic relationship?

Herbivory Signup and view all the answers

What is aposematic coloration primarily used for?

To warn predators to stay away Signup and view all the answers

Which of the following accurately describes Müllerian mimicry?

Two unpalatable species resemble each other Signup and view all the answers

What does species richness indicate about a community?

The number of different species in the community Signup and view all the answers

How does a community with even species abundance compare to one with unequal distribution?

It is more diverse because all species are equally represented. Signup and view all the answers

What do interspecific interactions primarily refer to?

Relationships between different species Signup and view all the answers

What is relative abundance in the context of species diversity?

The proportion of each species compared to the total individuals Signup and view all the answers

Which statement about species interactions in a community is true?

Interspecific competition can negatively affect one or both species involved. Signup and view all the answers

What defines the relationship in mutualism?

Both organisms benefit from the interaction. Signup and view all the answers

Which of the following best illustrates commensalism?

Birds nesting in the branches of trees without harming them. Signup and view all the answers

Which type of parasitism lives on the external surface of its host?

Ectoparasites Signup and view all the answers

What is the difference between obligate and facultative mutualism?

Obligate mutualism requires one species for survival, facultative allows both to survive independently. Signup and view all the answers

Which of the following is an example of an endoparasite?

Tapeworms residing within the intestines of animals. Signup and view all the answers

What is the primary factor that limits photosynthetic output in ecosystems?

The amount of solar radiation reaching the Earth's surface Signup and view all the answers

Which type of species has the highest biomass and can control the distribution of other species in an ecosystem?

Dominant species Signup and view all the answers

What role does primary production play in an ecosystem?

It establishes the energy budget for the ecosystem Signup and view all the answers

What describes the interconnected structure of food chains within an ecosystem?

Food webs Signup and view all the answers

What typically characterizes invasive species in a new ecosystem?

Lack of natural predators or disease Signup and view all the answers

What do predators use to improve their chances of capturing prey?

Claws, teeth, and poison as feeding adaptations Signup and view all the answers

Which of the following best defines aposematic coloration?

Coloration that warns predators to avoid prey Signup and view all the answers

In Batesian mimicry, which outcome occurs?

A harmless species mimics a harmful model Signup and view all the answers

What kind of adaptations do plants develop due to herbivory?

Mechanical and chemical defenses Signup and view all the answers

What is the relationship type for symbiosis?

Inter-specific relationship Signup and view all the answers

Which strategy is NOT typically used by prey to avoid predation?

Feeding adaptations against predators Signup and view all the answers

Müllerian mimicry involves which of the following?

Two or more unpalatable species resembling each other Signup and view all the answers

What can be a consequence of strong interspecific competition between two species?

Competitive exclusion of one species Signup and view all the answers

Which term describes the niche an organism occupies in the presence of competition?

Realized niche Signup and view all the answers

How does resource partitioning allow species to coexist?

By minimizing overlap in resource use Signup and view all the answers

What is the competitive exclusion principle also known as?

Gause's Law Signup and view all the answers

The total requirements of a species for all resources and conditions define which of the following?

Ecological niche Signup and view all the answers

Which of these scenarios best describes competitive exclusion?

One species completely outcompeting another for limited resources Signup and view all the answers

What is a key difference between fundamental and realized niches?

Fundamental niche is unaffected by competition, realized niche is not Signup and view all the answers

What typically allows coexistence of two species with identical ecological niches?

Resource partitioning through evolutionary changes Signup and view all the answers

Study Notes

Community Ecology

Community ecology studies the variety of organisms within a community.
Species diversity consists of two major components:
- Species richness: the total number of different species within a community.
- Relative abundance: the proportion of each species compared to the total number of individuals in the community.
Two communities can have the same species richness, yet a different relative abundance.
A community possessing an even species abundance is more diverse than one dominated by one or two abundant species.

Ecological Interactions

Interspecific interactions involve relationships between different species in a community.
Examples include competition (-/-), predation (+/-), herbivory (+/-), symbiosis (parasitism (+/-), mutualism (+/+), commensalism (+/0)), and disease.
Competition occurs when different species compete for a limited resource.
Competitive exclusion occurs when strong competition results in the elimination of one of the two competing species.
The ecological niche is the total use of biotic and abiotic resources by an organism in its environment.
The competitive exclusion principle (Gause's Law) states that two species competing for the same limiting resource cannot coexist in the same place.
Coexistence occurs when overlap between niches is reduced.

Experimental Evidence (Paramecium)

Species grown alone and together exhibit differing population densities over time.

Ecological Niche

The total requirements of a species for all resources determine where it can live.
The niche of an organism depends on location and behavior.

Fundamental and Realized niche

Fundamental niche: the potential ecological niche of an organism when competition is absent.
Realized niche: the niche an organism actually occupies in the presence of competition.
Examples show how competition can alter an organism's niche.

Resource Partitioning

Resource partitioning is the differentiation of niches that enables similar species to coexist in a community.
Competition between species with identical niches can result in species extinction.
Evolution by natural selection leads to the modification of resources utilized by one species.
This results from species evolving to use different resources, avoid competition and potentially coexist

Character Displacement

Character displacement is the tendency for characteristics to be more divergent in sympatric populations of two species.
Competing species evolve slightly different niches to avoid competition.
Reduces interspecific competition.
An example: variations in beak size between populations of two Galapagos finch species.

Predation (+/-)

Predation is the interaction where one species (predator) kills and eats another (prey).
Predators often possess adaptations to increase hunting success(claws, teeth, fangs, stingers, poison).
Prey often evolve adaptations to evade predators (camouflage, warning coloration, behavioral defenses).

Prey Strategies

Prey animals have evolved adaptations to evade predators.
- Behavioral defenses: fleeing, hiding, self-defense, alarm calls
- Alarm calls: summoning other prey to mob the predator
- Cryptic coloration (camouflage): making prey difficult to spot.
- Aposematic coloration: warns predators to stay away from prey (bright warning colors).
- Mimicry: resembling another species to deter predators (Batesian and Mullerian)

Batesian Mimicry

A palatable/harmless species mimics an unpalatable/ harmful model species.
Mimic gains protection from predators, while model gains no benefit.
Example: Hawkmoth larva mimicking poisonous species.

Mullerian Mimicry

Two or more unpalatable species resemble each other.
Predators learn to avoid the shared appearance. Example: Cuckoo bee and yellow jacket.

Herbivory (+/-)

Herbivory is the process in which an herbivore eats parts of a plant.
Plants have evolved mechanical (spines, tough leaves) and chemical defenses.
Herbivores have consequent adaptive responses to these plant defenses.

Symbiosis

Symbiosis is an intimate, long-term association between different species
Two main types:
- Parasitism (+/-): one species benefits at the expense of the other.
  - Endoparasites live internally within their host's body.
  - Ectoparasites live and feed externally on their host's body surface.
- Facilitation: one species benefits while the other remains unaffected or benefits.

Commensalism (+/0)

In commensalism (+/0), one species benefits, while the other is unaffected.
Example: Epiphytes growing on other plants for support.
Example: Clownfish and sea anemones.

Mutualism (+/+)

In mutualism (+/+), both interacting species benefit.
Can be obligate (one species cannot exist without the other) or facultative (both species can survive alone).
Example: Coral and zooxanthellae, Rhizobium and legume plants.
Example: Lichens: alga + fungus, alga provides food, fungus provides minerals and shelter.
Example: Mycorrhizae: plant + fungus.

Species with Large Impacts

Dominant species: most abundant or have highest biomass, exert powerful control on other species.
- Example: Sugar maple dominates North American forests.
Invasive species: introduced to a new environment by humans, often lack predators or disease.
Keystone species: exert strong control on community structure (even though not abundant). Removing a keystone species drastically alters the ecosystem structure.
- Example: Sea otters.
Foundation species (ecosystem engineers): modify their physical environment, altering it, enabling other species survival.
- Example: Beavers.

Ecosystems

Two concepts:
- Energy flow (refer to lecture 2)
- Cycling of chemical elements.

Primary Production

The amount of light energy converted to chemical energy by autotrophs.
Photosynthetic production limits the energy budget of the entire ecosystem.
Solar radiation limits photosynthetic output.

Food Webs

Food chains within an ecosystem interconnect in a food web.
Carnivores often consume multiple prey species.

Nutrient Cycles

Ecosystems involve the cycling of nutrients:
- Nitrogen Cycle: nitrogen fixation, ammonification, nitrification, denitrification
- Carbon Cycle: photosynthesis, cellular respiration, burning of fossil fuels, etc.
- Water Cycle: evaporation, transpiration, precipitation, runoff
- Phosphorus Cycle: weathering of rocks, leaching, uptake by plants, decomposition, consumption

Threats to Biodiversity

Includes images from the presentation.
Threats to biodiversity include habitat loss, pollution, overexploitation, introduction of invasive species, and climate change.

Species Diversity Endangerment

Gives example species of concern (Philippine eagle, Yangtze River dolphin, Javan rhinoceros)

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Description

Test your knowledge on species richness, diversity, and interactions within ecological communities with this quiz. Delve into concepts like mutualism, competition, and niche definitions, and explore the various types of species interactions that shape ecosystems.