Lecture 20

Question 1

Endangered Species Act of 1973

Answer 1

To “provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved and to provide a program for the conservation of such species”

Question 2

Endangered

Answer 2

Those likely to go extinct in all or a major portion of their range
-Currently 988 species endangered

Question 3

Threatened

Answer 3

Likely to become endangered in the near future

-Currently 276 species threatened

Question 4

Two components to measure species diversity

Answer 4

1) Species Richness
- Total number of species in an area
2) Species Diversity
- Takes into account both the number of species present and the relative distribution of individuals among species (evenness)

Question 5

Simpson’s index (D)

Answer 5

A single value that takes into account species richness and relative abundance of individuals among species
-D Ranges from 1-S (S= Species Richness)

Question 6

Ecological Succession

Answer 6

The processes and change in species composition following a disturbance in a community

Question 7

Types of Disturbances

Answer 7

Abiotic or Biotic (anthropogenic or natural)

• Natural (Fires, Floods, Tornadoes, Climate change, tree falls, etc)
• Human Activities (Logging, Mining, Clearing Land for agriculture)
• Events alter light levels, nutrients, unoccupied space, and other resources

Question 8

Primary Succession

Answer 8

The colonization of habitats devoid of life, occurs in a new habitat with no vegetation prior to succession
Ex) Glaciers, Volcanic Eruptions, Dune and barrier island formation

Question 9

Secondary Succession

Answer 9

-Occurs when a disturbance removes some or all of the organisms from an area but leaves the soil in tact
Ex) Volcanic eruptions, floods, fires, tree falls, logging, disease epidemics, landslides, etc

Question 10

What characteristics would you expect to find in organisms that initially colonize an area following a disturbance?

Answer 10

R-Selected

• Poor competitors, fast growing, short life spans, good colonizers, good dispersers, introduced species
• must be able to tolerate severe abiotic conditions

Question 11

What characteristics would you expect of find in organisms that inhabit an area that has been free of disturbances for a long time?

Answer 11

K-Selected

-Good competitors, long life spans, slower growing

Question 12

How can Existing species effect subsequent species?

Answer 12

1) Inhibition

2) Facilitation

Question 13

Inhibition

Answer 13

Species may inhibit colonization of other species; area made less suitable for later species
-Competition: using nutrients or water, taking up space, shading other species, releasing secondary compounds.

Question 14

Facilitation

Answer 14

Species may facilitate the appearance of other species; earlier species modify the environment which makes it easier for other species to move in
-Increases nutrients by dropping leaves, nitrogen-fixing bacteria, change pH of the soil, make soil more fertile, create shade