Chapter 8 Flashcards
Properties of a Population (Unit 2)
A populations density is calculated as the…
number of individuals per unit area
How might a species’ range be extended?
through climate change
The sex ratio of human senior citizens (>65 years) is…
a. 1:1
b. skewed towards females
c. the same as birds’
d. skewed towards males
skewed towards females
Which of the following represents a modular organism?
a. coral
b. dog
c. lizard
d. ant
Coral
Which of the following sampling techniques represents an index of abundance rather than an estimate of density?
number of bear droppings along a trail
The demographic age pyramid of a rapidly growing population is…
wide at the base, narrow at the top.
Why is Pacific salmon movement into freshwater streams considered migration if the salmon die at the head of the stream and never return to the ocean?
a. It is not migration but immigration
b. Most male adult is survive reproduction and return to the ocean
c. Migration is a one-way movement
d. Because their offspring returns to the ocean, so the entire population participates in the migratory event via different life stages.
Because their offspring returns to the ocean, so the entire population participates in the migratory event via different life stages.
If more individuals move out of a forest than into it every year, the ____ rate is high
emigration
A module that is produced asexually by an original genetic individual, which may either remain physically linked to the parent or may be separated, is referred to as a(n)…..
Ramet
Calculate the estimated population size (N), given a study that initially marked 100 animals and subsequently captured 50, of which 25 were already marked.
N = 200
Define population
Group of individuals of the same species that inhabit a given area. Populations have structure, are dynamic, and change over time.
Define distribution
The area over which the population occurs
Define geographic range
The range of which an individual of a species can live.
What is geographic range limited by? (give 4 examples)
A species tolerance to different environmental conditions (temperature soil moisture, elevation, geographic barriers).
Define ubiquitous species
Species with a geographically widespread range/distribution
Define endemic species
Species with a geographically restricted distribution. Many have specialized habitat requirements. High rate of extinction.
Why aren’t organisms distributed equally across a geographic range?
Organisms are found within suitable habitats within that range. The environment is heterogeneous, so some habitats are suitable and others are not within this range.
How are populations divided into subpopulations while remaining connected?
Populations are divided into subpopulations that live in suitable habitat patches surrounded by unsuitable habitats. These subpopulations are spatially separated but connected by the movement of individuals between them (immigration/emigration).
Define metapopulation
Collection of local subpopulations
Define abundance
Defines the size of a population (# of individuals).
A function of population density and the area over which the population is distributed.
What is a quadrat?
A grid search for population distribution
What is Crude Density? and what is the metric for it?
The number of individuals per unit area. Use m2, km2, or kL, L.
How do you perform a quadrat?
Place a grid over an area. Find the amount of an organism within this grid and calculate the density based on the area of the grid.
Which test is better for determining plant density? animal density?
Plant - quadrat
Animal - mark-recapture
Define random distribution
Position of one individual is independent on the position of another individual
*quadratting works very well for this type
Define uniform distribution
Organisms are found at a regular distance from one another
Define clumped distribution
Individuals are found in groups. The presence of one individual predicts the presence of another.
Define ecological density. What is a downside of it?
Number of individuals per unit of available living space. Helps to account for patchy distributions of some species.
Downside - difficult to determine what part of a habitat is living space for a specific species.
Population abundance formula
Population abundance = (population density) x (area occupied)
What is the mark-recapture method?
Capture a number of individuals in a population within x amount of time. Mark them. After an appropriate period of time, capture a number of individuals within the same amount of time.
Of the individuals captured the second time, some will have been marked or recaptured.
Use the numbers to determine population density
What is the formula of mark-recapture and what the variables mean?
N = nM/R
N = Population size
M = originally captured individuals
n = total individuals captured on 2nd trip
R = individuals recaptured on 2nd trip
What are the 3 cohorts a population can be divided into?
Pre-reproductive
Reproductive
Post-reproductive
How can we determine their relative age of death? (what do we look at)
- wear of teeth / teeth replacement
- growth rings in teeth or horns
- plumage changes/ wear&tear of plumage in birds
- annual growth rings
What do the pyramids of the 3 age distributions look like?
Positive growth rate - pyramid with a wide base - represents growing population
negative growth rate - pyramid with a narrow base - represents dying population
no growth rate - equal base to top - represents static population
How does the sex ratio shift for organisms throughout life? (birth - post-reproductive)
Sex ratio at birth is slightly shifted towards males (1.07:1) but shifts towards females in older age.
Why do males generally have a shorter lifespan than females?
Males typically have rivalries for resources/mates, resulting in a greater likelihood of death
Define dispersal
Movement of individuals in space
Define emigration / immigration
emigration - individuals exit a subpopulation
immigration - individuals join a subpopulation
Define passive & active dispersal
Passive - abiotic factors move individuals
Active - individuals move themselves
