Ecology Chapters 44-47

Question 0

Define and distinguish between density and dispersion.

Answer 0

​Both may be used to describe population, but density is the number of individuals per unit area or volume, while dispersion is the pattern of spacing among individuals within the boundaries of the geographic population.

Question 1

Define the scope of population ecology.

Answer 1

Population ecology allows us to examine and analyze the structural and dynamic aspects of population. The concepts may be applied to specific populations, metapopulations (populations of populations), and the human population on Earth.

Question 2

Explain how ecologists measure the density of a species.

Answer 2

​In some rare cases, all the individuals in a population may be counted, but many times, ecologists must use a variety of sampling techniques to estimate densities. For example, they might count the number of individuals in several randomly located plots of the same size, then extrapolate (conclude) their data. They may also estimate densities using an index (indicator) of population size, such as the number of nests, burrows, tracks, or fecal droppings.

Question 3

Describe conditions that may result in the clumped dispersion, uniform dispersion, and random dispersion of populations.

Answer 3

Clumped Dispersion: Influenced by resources and behaviors -> Areas were there are several animals in a group -> Ex. Wolves

Uniform Dispersion: Evenly spaced out -> Ex. Penguins

Random Dispersion: Independent of other individuals -> Ex. Dandelions (There seeds blow everywhere in no specific pattern

Question 4

Describe the characteristic of populations that exhibit Type I, Type II, and Type III survivorship curves.

Answer 4

Type I: Live until they are old and then they die -> Usually have few offspring -> Ex. Humans

Type II: In the middle of Type I and III -> Ex. Fish and sea life

Type III: Either die off at a young age or if they survive they will live a long time and then die -> Usually have many offspring

Question 5

Compare the age structures of Italy, Afghanistan, and the United States. Describe the possible consequences for each country.

Answer 5

Italy- In Italy, more people die later on in their lives leading to the fact there are more old people.

Afghanistan- The people die in their early years. Most people die in their first 4 years of life.

United States- Like Italy, most people die in their later years of life

Question 6

Define and distinguish between semelparity and iteroparity.

Answer 6

Semelparity: Reproduce once and then die afterwards

Iteroparity: Reproduce repeatedly

Question 7

Distinguish between exponential and logistics growth.

Answer 7

Exponential model: J-shaped

Logistic model: sigmoid S-shaped, carrying capacity

Question 8

Explain how density-dependent factors affect population growth and how density-independent factors affect population growth.

Answer 8

Density-dependant factors, Biotic factors (competition, predation, disease, parasitism):
•Birth rate decreases when a population increases
•Death rate increases when a population increases

Density-independent factors, Abiotic factors (related to weather and climate):
•may periodically wipe out large numbers of organisms or even may decimate populations in a certain area.

Question 9

Know the characteristics of r-selected and K-selected populations

Answer 9

r-selected populations: Density-dependent selection; it selects for life history traits that are sensitive to population density

K-selected populations: Density-independent selection; it selects for life history traits that maximize reproduction

Question 10

Explain the relationship between species richness and species diversity.

Answer 10

Species richness - list of organisms

Species diversity - list of organisms and abundance

Question 11

Be able to discuss the island biogeography model.

Answer 11

The larger the conserved area, the better the chance of preserving more species.

Larger islands: Higher immigration rates, more diverse, low extinction rate, animals are more likely to find

Smaller islands: Lower immigration rates, less diverse, high extinction rate, animals less likely to find

Close islands: larger immigration rates

Far islands: Lower immigration rates

Question 12

Describe the competitive exclusion principle and how competitive exclusion may affect community structure. Also know how resource partitioning and character displacement help competing organisms.

Answer 12

Competition for a resource can eliminate a competing species. This eliminated species may play a critical part to the community of the ecosystem.

Resource partitioning: Coexistence among species that need the same resource by sharing said resource.

Character displacement: Divergence among species that lessons the competition; the same species of bird, but one has a larger beak making it able to eat larger seeds and leaving smaller seeds to the birds with smaller beaks.

These two factors help competing organisms by allowing them to coexist and not be eliminated.

Question 13

Define and compare predation, herbivory, and parasitism.

Answer 13

Predation: interaction where one species (the predator) kills and eats the other species (the prey). +/-

Herbivory: interaction in which a herbivore eats parts of a plant or algae. +/-

Parasitism: interaction where one organism (the parasite) derives nourishment from another organism (the host) which is harmed in the process. +/-

Question 14

Distinguish between primary and secondary succession.

Answer 14

Primary succession involves the invasion of living organisms in an area that had no previous existing community or soil.

Secondary succession occurs in places where the established community has been damaged or destroyed either by human activity or natural processes.

Question 15

Dynamics of an ecosystem

Answer 15

Trophic levels: Trophe 1 is Autotrophs, Trophe 2 is heterotrophs

Food chains link the species in the food web

Biomass is material derived from living, or recently living organisms

Food webs depicts feeding connections

Energy flow moves up giving the next level 10% while the other 90% is heat
Chemical cycling

Question 16

Describe the relationship between autotrophs and heterotrophs in an ecosystem.

Answer 16

Producers convert sunlight into organic chemical energy and heterotrophs utilize that stored energy.

Question 17

Explain how decomposition connects all trophic levels in an ecosystem.

Answer 17

Decomposition returns all of the nutrients from organisms of all tropic levels back to earth.

Question 18

Explain how the first and second laws of thermodynamics apply to ecosystems.

Answer 18

First law states that energy cannot be created nor destroyed, but rather simply changes form. The change in an ecosystem’s form of energy is related to the ecosystems heat (by the growing and dying of organisms) and work (also by the growing and dying of organisms), and as an ecosystem grows and dies, the form of energy in the ecosystem changes.

Second law states that in any energy transfer, some energy is lost as heat.

Question 19

Biomagnification

Answer 19

The accumulation of pollutants as they move up the food web.

Example: DDT pesticides sprayed on crops, crops being eaten by cow, humans eating cow -> it goes from one organism to another and another

Question 20

Know the definition of conservation biology and bioinformatics.

Answer 20

Conservation biology: discipline that seeks to understand the effects of human activities on species, communities, and ecosystems and to develop practical approaches to preventing the extinction of species and the destruction of ecosystems

Bioinformatics: Area of scientific study that utilizes computer technologies to analyze large sets if data

Question 21

Know the importance of genetic diversity to species survival.

Answer 21

All members of a species have different mutations and traits that desperate them from each other, making them diverse. If these traits did not exist, something (such as a virus) that kills one member of a species may kill all members of the species due to them not having any genetic diversity whatsoever.

Question 22

What is the keystone species. know an example and how its removal affects the ecosystem.

Answer 22

Keystone species: Species whose activities significantly affect community structure.

Elephants in grasslands yank out young trees, or eat the growth points off of their branches. This stops the progression of grassland to forest.
If elephants were removed from grasslands, the trees would grow and reproduce eventually taking over the grasslands and converting them into forests, killing off the antelope that need grass to survive and the predators, such as tigers that need the antelope to survive.