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APES - Ch. 6 Lecture Questions
Community and Population Ecology
Terms in this set (37)
Explain the two components of species diversity.
1. species richness - the number of different species
2. species evenness - the relative number of individuals within each species
Why do you think species diversity is an important characteristic of a community?
A hypothesis exists that a species-rich community is more sustainable and productive than one that is not as diverse because complex communities result in a variety of feeding paths and has more ways to respond to environmental stressors.
Describe the species richness and species evenness of a coral reef compared to an evergreen forest.
1. In a biologically diverse community such as a coral reef, there are a large number of species (high species richness), but often few members of each species (low species evenness)
2. An evergreen forest community in Alaska may have a few different plant species (low species richness) but large numbers of individual plants (high species evenness.)
Describe the niche structure and its importance in a community.
Niche structure, or the ecological roles each species plays in an ecosystem, is characterized by:
- how many ecological niches occur in an area
- how they resemble or differ from one another
- how species from different niches interact
Importance: Since certain roles much be fulfilled for a particular ecosystem to be sustainable, threats to particular niches can threaten the stability of an entire ecosystem.
Explain how geographic location influences or is related to species richness.
Species richness, the variety of species, tends to be highest near the equator/tropics and declines as we move toward the poles.
Distinguish among the three aspects of stability.
1. inertia/ persistence - the ability of a living system to resist being disturbed or altered.
2. constancy - the ability to keep populations within the limits imposed by available resources.
3. resilience - the ability of a living system to repair damage after external disturbance.
Give an example of an ecosystem with high inertia and explain why this is so.
Tropical rain forests have high inertia because they have many different species resulting in a number of feeding paths and more ways to respond to environmental stresses allowing them to resist significant alteration or destruction as long as large areas are not degraded.
Give an example of an ecosystem with high resilience and explain why that is so.
Grasslands have high resilience because most of their plant matter is stored in underground root systems, which repair themselves and recover after destruction such as burning. Grasslands can only be destroyed if their roots are removed.
What are the names given to other species that migrate into or are deliberately or accidentally introduced into a community?
nonnative / invasive / alien species
Give some examples of useful nonnative species.
1. domesticated crops, such as corn increased an additional food resource for people an animals in areas where it was introduced.
2. Domesticated animals - chickens, cattle and horses - have provided food, transportation and labor resources for human populations on various continents where they were introduced
Describe some negative effects of invasive species.
- sometimes the environment cannot adapt to a new species takeover
- if there are no natural predators, nonnative populations can grow out of control
- nonnative species can change the food web by preying on native species or competing against native species for food or other resources
- decreasing biodiversity by preying on or killing native species
- changing the conditions in the ecosystem, such as soil chemistry
Discuss some of the conditions or characteristics that favor invasive species.
- no natural predators or diseases
- similar niches to their native habitat
- better able to compete against the native species in the new environment
Why are birds excellent indicator species?
1. exist almost everywhere
2. respond quickly to environmental changes such as loss or fragmentation of habitat
3. affected quickly by the introduction of chemicals such as air and water pollution or peticides
Why are amphibians excellent indicator species?
1. live part of their lives in the water and part on land, so they are especially vulnerable and sensitive to environmental disruptions
2. eat plants early in their life cycle and insects late in their life cycles, so they are exposed to the effects of contamination to both
3. have no protective shells or hair to block UV radiation or pollution
4. take in water and air through their highly permeable skin, so they absorb and show the effects of pollutants in the air, water and soil
Give an example of a keystone species and all of the important ecological roles it fills in its niche
1. dig gator holes which hold freshwater during droughts and supply food and water for many terrestrial and aquatic species in the wetlands.
2. They also hunt many predatory fish such as gar, providing a balance that keeps these fish from hunting other species of fish to extinction.
3. when they nest, on gator mounds, they keep open water areas free of invasive vegetation that would choke out and fill in coastal wetlands and freshwater ponds, which provide habitats for many other species.
If suddenly the world had no bees, what are some of the possible effects?
- serious reduction of flowering plants from lack of pollination (1/3 of agricultural crops are dependent on bee pollination)
- worldwide food shortages for humans as well as animals
- massive economic consequences to those who grow and buy agricultural crops
Give an example of a foundation species and the functions it provides in a community
Beavers create wetlands by felling trees along shorelines and using them to build dams across streams, which create habitats for both terrestrial (especially birds and insects) and aquatic species.
Birds and bats provide reforestation of depleted areas by dropping fruit and plant seeds, which provides habitat for many forest species.
What is the difference between a keystone species and a foundation species?
A foundation species provides the habitat that allows the ecosystem to exist. A keystone species keeps the ecosystem sustainable. (So beavers may create wetland areas that alligators live in and maintain for other species in the ecosystem to survive.)
Explain the competitive exclusion principle.
states that two species competing for the same limiting resource cannot coexist. One species will perform better and drive the other to extinction.
What are some different ways that species reduce or avoid competition with other species?
Example #1: When lions and leopards live in the same area, lions will focus on taking larger prey while leopards will take smaller prey.
Example #2: Hawks and owls hunt similar prey, but hawks hunt during the day and owls hunt at night.
Example #3: Different species of warblers, which all eat insects, have adjusted to eat insects from specific parts of a spruce tree.
insects from specific parts of a spruce tree.
What is resource partitioning?
when organisms use resources at different times, in different ways, or in different places in order to avoid competition
Compare and contrast predator strategies to prey strategies.
carnivores employ different ways to capture prey:
1. pursuit - running after animals
2. ambush - jumping out and surprising other animals
3. camouflage - to hiding themselves in plain sight
4. chemical warfare - using poisons or anesthetics to subdue prey
prey species have evolved many ways to avoid predators:
1. running, swimming or flying away fast
2. protective outer coverings such as: shells, thick bark, and spines
3. camouflage - examples: chameleons and cuttlefish
4. chemical warfare - including poisonous, irritating, foul-smelling, and bad-tasting
5. warning coloration, examples: monarch butterflies
6. mimicry - acting like or appearing like a dangerous or unpleasant animal
7. behavioral strategies, such as spreading wings, puffing up, and living in large groups
What is predator-mediated competition?
when predation on one species reduces competition among that species' competitors (Ex: Wolves preying on elk, so the elk population declines, and as a result, the beaver and bison population in the community increase)
What conditions lead to competition?
1. limited food and water resources
2. limited usable space
3. overgrowth or increasing population
4. territorial behavior
5. invasive species
How would a scientist determine if two species were competitors?
Remove/reduce one key element from the food web and observe the effect on the population of two species.
Which relationships from the chart given are not symbiotic?
Because the definition of symbiosis applies to any type of persistent biological interactions (i.e. mutualistic, commensalistic, or parasitic); the only relationships from the chart that are not symbiotic would be: completion, and ammensalim and neutral.
What is the difference between interspecific and intraspecific competition?
Interspecific - competition among members of different species
Intraspecific - competition among members of the same species
What are parasitoids?
organisms that lay their eggs inside other organisms Ex: roundworms, heart worms
What is the difference between primary and secondary succession?
1. Primary succession - establishment of communities in a lifeless area devoid of soil (on land) or sediment (in water). Examples: bare rock, abandoned parking lots, newly created ponds; takes a long time -thousands of years.
2. Secondary succession - in an area where communities once lived but were disturbed or destroyed, but where soil or sediment remain. Examples: burned or cut forests, heavily polluted streams
Describe the NPP and nutrient cycling of ecosystems undergoing succession.
Frequent but moderate disturbances that lead to succession promote population control and increase the complexity of the food webs for energy flow and nutrient cycling necessary for sustainable biodiversity.
Give two examples of a location that would undergo secondary succession.
1. burned or cut forests
2. heavily polluted streams
What are different types of population dispersion?
1. clumping (most common)
2. uniform dispersion
3. random dispersion
Give two examples of density dependent factors that affect growth.
density dependent factors depend on the population density - ex: food and migration
Give two examples of density independent factors that affect growth.
density independent factors do not depend on the population density and are usually abiotic - ex: flash flooding, wild fires
Explain the importance of carrying capacity as a means of regulating population growth.
Maximum number or organisms that the environment will sustain. As a population nears the carrying capacity, the growth rate will begin to decrease because available resources begin to dwindle.
Differentiate between r-selected and k-selected species.
r-selected species - (opportunists) have a high rate of population increase (r ) - many small off-spring, most of which do not survive to reproduce; subject to J-shaped growth curve (boom and bust growth) Ex: mosquitoes, snails
k-selected species - (competitors) have a steady rate of population increase and reach their carrying capacity; few large off-spring, most of which live to reproduce; fairly long lifespans; S-shaped growth curve Ex: elephants, primates
What are the five basic types of species interaction?
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