unit 3- populations

population

group of organisms of the same species that inhabits a defined geographic area at the same time

population density

refers to number of individuals of population that inhabit a certain unit of land or water area

population dispersion

refers to how individuals of a population are spaced within a region

uniform

members of population uniformly spaced throughout geographic region, often result of competition for resources in ecosystem

random

position of each individual is not determined or influenced by the positions of the other members of the population, relatively uncommon dispersion

clumped

most common dispersion pattern, individuals flock together

biotic potential

population is the amount that the population would grow if there was unlimited resources in its environment, not practical model

carrying capacity (K)

maximum pop. size for the species that can sustainably be supported by the available resources in that environment

exponential population growth

rate is seen where resources are unlimited, but rare in nature

logistic population growth

populations well below carrying capacity → exponential growth, approach carrying capacity → population shrinks

overshoot

def: when population exceeds carrying capacity

effects: resource depletion, carrying capacity may be lowered, dieback of pop, lack of available resources → famine, disease, conflict (they can recover from this or not)

Rule of 70

the time it takes, in years, for pop. to double can be approximated by dividing 70 by the current growth rate of the pop.

doubling time

amount of time it takes for pop. to double

r-selected organisms

species that prioritize rapid reproduction by producing a large number of offspring with minimal parental care, often adapting to unpredictable environments, competition for resources low

K-selected organisms

species that produce relatively few offspring but invest a lot of parental care, thrive in stable environments, high competition in environment for resources

survivorship curves

represent the # of individuals in a population born at a given time that remains as time goes on

cohort

refers to the # of individuals in a population born at a given time

type I

indicates that most individuals in the population survive into adulthood with sharp increase in mortality as the population approaches the species’ maximum age

type II

mortality and survival rates are fairly constant throughout life

type III

most offspring die, but if live to a certain age they will live longer life

boom-and-bust cycle

rapid increase in the population and equally rapid drop off

density-dependent factors

environmental factors that affect a population's size and growth based on its population density (birth and death rates, increased predation, competition for food, disease, buildup of toxic materials)

density-independent factors

change population’s size regardless of whether the population is large or small (catastrophic events)

crude birth rate

number of live births per 1,000 members of the population in a year

crude death rate

number of live deaths per 1,000 members of the population in a year

Actual Growth Rate

equals (birth rate-death rate)/10

emigration

movement of people out of population

immigration

movement of people into a population

total fertility rate (TFR)

used to describe the number of children a woman will bear during her lifetime, determined through analysis of data from previous years

replacement birth rate

number of children a couple must have to replace themselves in a population, higher mortality rate → higher replacement rate

infant mortality rate

number of deaths of children under 1 years old per 1000 live births

age-structure pyramids/diagrams

useful for graphically representing populations, can be used to predict population trends

pre-reproductive

division of humans in age diagram, 0-14 years old

reproductive

division of humans in age diagram, 15-44 years old

post-reproductive

45 years old and older

population momentum

phenomenon where a population continues to grow even after fertility rates drop below replacement level, primarily due to a large portion of the population being in their reproductive years, meaning a large number of young people are still having children despite the lower birth rate per woman

Malthusian catastrophe

idea that humans might overshoot carrying capacity of Earth as a whole and suffer some sort of catastrophe

demographic transition model

used to predict population trends based on birth and death rates of a population

demographic transition

population moves from first state to second state

preindustrial state

population exhibits a slow rate of growth and high birth and death rate because of harsh living conditions

transitional state

birth rates are high and because of better food, water, and health care death rates are lower. Birth rates remain high due to cultural or religious traditions and lack of education for women

industrial state

population growth high, birth rate drops becoming similar to death rate, many developing countries in this state

postindustrial state

population approaches and reaches zero growth rate, may drop below zero growth rate

genetically modified organisms (GMOs)

controversial, inserting strands of DNA that code for resistance to pests, leads to less genetic diversity and crops can be more likely to be susceptible to future pests and diseases

macronutrients

nutrients needed in large amounts (vitamin, iron, calcium)

micronutrients

essential vitamins and minerals required in small but critical amounts for their healthy growth and development

hunger

a biological need for food, a physiological sensation of discomfort or pain caused by a lack of sufficient dietary energy, which can lead to malnutrition if prolonge

malnutrition

poor nutrition from insufficient or poorly balanced diet

undernourished

description of person who has not been provided with sufficient quantity or quality of nourishment to sustain proper health and growth

food deserts

a low-income area with limited access to affordable and nutritious food