Week 3 and Week 4 Flashcards
geographic range
describes where individuals of a species might be located
cosmopolitan species
an extreme, worldwide in distribution
endemic species
found in only a small restricted area.
factors determining the geographic range of a species
history
biological tolerances
other species
or a combination of the above
examples of physiological factors limiting distribution
palms- widespread through tropics and subtropics but are absent where winter temps go below freezing This is because the “hearts of palm” occur at the top of the trunk and are not tolerant of freezing
Also their seeds are water-dispersed, and can live in the ocean for months therefore coconut palms tend to occur on beaches or close to waves
Historical factors determing range of a species (an example)
A “Gondwanan” distribution from the supercontinent when continents no longer touching used to touch eachother.
populations
groups of individuals livingina habitatatagiventime
the number of individuals in the population at any given time
size or abundance
The number of individuals in the population per unit area or unit volume
density (for many organism it is the density of the population rather than it’s actual numbers that exerts a real effect on the organism)
Clumping
Clumping sometimes occurs because some areas of the habitat are more suitable than others (ex- salamanders clumped under fallen logs in the forest or plants clumping because of where seeds fall)
Random distribution
Uncommon
Occurs in the absence of strong attraction or repulsion among individuals
Regular distribution
Generally happens because of interactions of individuals in the population (competition, territoriality, human intervention)
Age structure
The number of individuals at different ages
Sex ratio
The proportion of individuals of each sex ( the number of females is more important in the growth rate of populations)
variability
Differences among individuals in the population
ex- sexual dimorphism, metamorphosis
Many organisms exist as interwoven collections of subpopulations-the total is called a
metapopulation
Metapopulations
exhibit their own dynamics, with localized extinction, and recolonization of unoccupied areas of suitable habitat, determining their dynamics. (example cliff nesting birds and fresh water fish)
Formula for exponential growth
N_o*e^rt (where t is time r is the rate and N_o is the initial population size)
Carrying capacity
Populations grow until one or several limiting resources become rare enough to inhibit reproduction so that the population no longer grows
Limiting resources
Can include light, water, nesting sights, nutrients, prey etc
Density-Independent factors for limiting population growth
Independent of population size (ex- winter temperatures affect grasshoppers)
In the logistic growth model what is k? and what is N?
K is Carrying capacity
N is the number of individuals in the population at a given time
When N>K what happens to the populations?
They decline
Demography
The study of the age structure and growth of populations. Essentially the study of birth, reproduction, and death as it relates to populations.
Thomas Mathus
A famous early demographer. Reached the conclusion that human populations tend to grow until the have outstripped their food supply. (why are there always poor people?)
Complete enumeration
count every individual in the population
R_o
the rater of population growth or decline per capita
Survivorship curve
traces the decline of a group of newborns over time (plots the probability of surviving to a certain age)
Survivorship curve Type I
A convex curve. Most individuals will live to adulthood with most mortality occuring during old age.
Survivorship curve Type II
A straight line. An individuals chance of dying is separate from it’s age (ex-small birds)
Survivorship curve Type III
A concave curve. few individuals live to adulthood, the chance of dying decreases with age (ex-snapping turtles and redwood trees)
Current age structure of Africa
More young people than old people. Populations will increase in the future
Life history
timing of an organisms life and death
fitness
How many offspring an organism produces that are ultimately able to produce their own offspring.
Semelparity
One large reproduction effort (example most insects and annual plants)
Interoparity
Fewer offspring reproductive episodes (example perrenial plants and most large mammals)
Clutch size
The number of offspring per reproductive episode
