Chapter 18- Populations Flashcards
Ecology
The study of relationships that organisms have with each other and the environment.
Organism (single living indivdual)–> Population (a group of the same species of organisms living at the same place and time)–>
Community (all populations that occupy the same area)–> Ecosystem (the living and nonliving things of an area)–> Biosphere (global ecosystem/ all parts of earth and its atmosphere where life is possible)
Habitat
Location where an individual normally lives
Population density
Measure of the number of indivduals per unit area or volume of habitat
How you measure:
-simple counts
-mark-recapture method (capture, mark-em, release, recapture, count how many with tags)
Birth rate
Number of births per unit time, scaled by population. Depends on factors like age structure (distribution of age classes in a population) –> a population with a large number of prereproductive individuals will typically grow. Typically, the earlier the reproduction, the faster population will grow.
Death rate
Number of deaths per unit time, scaled by population size
Life table
shows the number of survivors remaining at each age
Survivorship curve
Life table values are plotted on a survivorship curve, a graph of the proportion of surviving individuals at each age. Curve follows three general patterns:
Type 1: Late loss (humans and large vertebrates)
-invest lots of time &energy in small number of offspring
-live long & death rate is highest as individuals approach maximum life span
Type 2: Constant loss (many birds and mammals)
-parental care
-threats of predation and disease are constant (could die at any age!)
Type 3: Early loss (many fishes, most invertebrates and plants)
-produce many offspring but invest little time in each one (they die young)
Life history
Includes all events from birth to death, but typically emphasized the factors that affect reproduction. Reproductive strategies fall into patterns shaped by natural selection:
Opportunistic life history (r-selected):
-high reproduction rate
-many offspring
-each offspring receives little parental care
-low survival rate among juveniles
-early reproductive maturity
-Type III survivorship curve
Equilibrium life history (k-selected):
-low reproduction rate
-few offspring
-each offspring receives extensive parental care
-high survival rate for juveniles
-later reproductive maturity
-Type I survivorship curve
Exponential growth
number of new individuals is proportional to a population’s size; this is, the larger the population, the faster it grows (repeated doubling ex., 1, 2, 4, 16, 32,…). It is a j-shaped curve.
Logistic growth
Competition, predation, and other factors will reduce birth rate and increase death rates, and the population might stablize at the carrying capacity (the maximum number of people that the ecosystem that support indefinately). When growth stops and carrying capacity approaches, it is called logistic growth. It is a S-shaped curve.
Density-dependent factors
Conditions whose growth-limiting effects increase as the population increases. Ex. diseases, predation, competition (factors are biotic, or living)
Density- independent factors
Factors that are unrelated to population density ex. natural disastors, severe weather, industrial accidents, habitat destruction (factors are abiotic, or nonliving)
