Unit 5 (ISU) Flashcards
population size (N)
the number of individuals of the same species living within a specific geographical area
population density (Dp)
the number of individuals per unit of volume or area
counting each individual within a population is impractical. how do ecologists use other methods to estimate population size and density? (in general)
sampling several smaller areas and applying the results to an entire area occupied by a species
transect
a long, relatively narrow rectangular area or line used for sampling a population
researchers choose a line of specific length, randomly determine a starting point and the direction they will travel. the researcher walks its length, counting the species being monitored and records individuals within a certain distance of the transect line
useful when density of a species is low, or when individual organisms are large, ex. trees
quadrat
an area of specific size used for sampling a population; often used to sample immobile organisms or those that move very little
several sample sites are randomly chosen and quadrats of a known size are marked. the number of individuals within the boundaries is counted
useful for sampling plant populations and those of sessile animals
to determine population density, calculate the sum of individuals in quadrats and divide by total area of quadrats
size of population can be estimated by extrapolating the density to the entire study area
quadrat population density equation
Dp=N(sum of individuals in quadrats)/A (area of quadrats)
mark-recapture
a method in which animals are captured, marked with a tag, collar, or band, released, then recaptured at a later time to determine an estimate of population size
useful for highly mobile populations, such as fish or birds
mark-recapture population size equation
N=(# of originally marked)(total individuals in recapture)/marked individuals in recapture
distribution pattern
the pattern in which a population is distributed or spread in an area; three types are uniform, random and clumped
two main factors that influence distribution patterns
the distribution of resources such as food and water within a habitat
the interactions among members of a population or community
clumped distribution
results from the tendency for populations to gather near unevenly distributed resources ex. animals gather near a water source, and plants cluster in locations with optimal moisture, temp and soil conditions
common among species in which individuals gather into groups for positive interactions (ex. protection from predators; increase hunting efficiency)
uniform distribution
exhibited in situations where resources are evenly distributed but scarce, and is often a consequence of competition between individuals
can be seen in plants competing for resources as well as in birds of prey and other organisms that behave territorially to defend food and shelter needed for survival, mating, or raising young
usually a result of negative interactions among population members (in contrast to clumped distribution)
random distribution
exhibited if resources are plentiful and uniformly distributed across an area because there is no need for individuals to defend their share
requires that interactions between individuals are neutral
distribution patterns displayed by a population are ____ and can _____ with the passing seasons or even over the course of a day
fluid, change
what forms distribution patterns
complex interactions between behaviors and other characteristics that increase each individual’s chances of reproduction and survival; ex. seasons changing and life stages in organisms
life history
the survivorship and reproductive patterns shown by individuals in a population
include the age at which an organism is sexually mature (when it can reproduce), how often it reproduces, how many offspring it has at a time, and life span
two main measures to describe life history
fecundity and survivorship
fecundity
the average number of offspring produced by a female member of a population over her lifetime
affected by age at which an organism becomes sexually mature
the # of offspring tends to be inversely related to the amount of care parents provide
survivorship
the number or percentage of organisms that typically live to a given age in a given population
ecologists study survivorship by studying a large group of individuals all born at the same time, monitoring the group over its lifetime, and recording the age of death for each organism
3 general patterns of survivorship
type III: most individuals die as juveniles (perhaps even before they sprout, hatch or are born). only few live to produce offspring or to old age. however, they can produce large #s of offspring. ex. oysters, many insects, plants, invertebrate organisms
type I: opposite of type III. high rate of juvenile survival, individuals live until sexual maturity and beyond. ex. humans, most mammals
type II: lies between I and III. risk of mortality is constant through an individuals lifetime
immigration
the movement of individuals into a population
emigration
the movement of individuals out of a population
in most population, immigration and emigration are roughly ______. ecologists tend to focus only on _____ and ______ when considering how populations size changes.
equal, birth, death
change in population size equation
deltaN=B(# of births)-D(# of deaths)
population change with immigration and emigration equation
deltaN=[B+I]-[D+E]
rate of population growth equation
gr (growth rate) = delta N/delta T
benefits of measuring growth rate
useful for populations that are expanding quickly, and for populations that may be endangered
can help ecologists make management decisions
growth rate does not take into consideration how the initial size of the population may affect population growth. explain
as long as nothing limits it, the growth of a larger population will always be greater than that of a smaller population, since this population typically has more individuals that can reproduce
capita growth rate equation
cgr=deltaN(# of individuals)/N (original # of individuals)
biotic potential
the highest possible per capita growth rate for a population
the factors that determine a species biotic potential are all related to its fecundity and include
the # of offspring per reproductive cycle
the # of offspring that survive long enough to reproduce
the age of reproductive maturity
the # of times the individuals reproduce in a life span
the life span of the individuals
exponential growth
the growth pattern exhibited by a population growing at its biotic potential
why can’t a population grow at its biotic potential
resources will quickly become limited. eventually, members of the population will compete for resources and the growth rate will slow
carrying capacity
maximum population size that a habitat can sustain over an extended period of time
logistic growth
the growth pattern exhibited by a population for which growth is limited by carrying capacity, or limited availability of resources
what happens as a population starts to grow in size
limiting factors such as disease, predation, and competition for resources reduce the amount of energy that is available for reproduction. this causes the growth rate of the population to decrease
why is carrying capacity not a static condition
it changes as the population responds to changing conditions such as a decreasing oxygen supply in a pond, low food supply during winter, disease, predation and limited space
what are life strategies
strategies to maximize the number of offspring that survive to a reproductive age
r and k
most populations are somewhere between the two groups. properly describing whether a population uses an r- or K- selected life strategy requires that it be compared to another population
r-selected strategies
life strategies used by populations that live close to their biotic potential
in general, species that have an r-selected strategy:
-have a short life span
-become sexually mature at a young age
-produce large broods of offspring
-provide little or no parental care to their offspring
ex. insects, annual plants and algae
they take advantage of favourable environmental conditions, such as the availability of food, sunlight and warm temp. to reproduce quickly.
they experience exponential growth during the summer, but die in large numbers at the end of the season
K-selected strategy
life strategies used by populations that live close to the carrying capacity of their environment
in general, species that have a K-selected strategy:
-have a relatively long life span
-become sexually mature later in life
-produce few offspring per reproductive cycle
-provide a high level of parental care
ex. mammals and birds
density-independent factor
an abiotic event that affects population growth in the same way, regardless of population density. ex. weather, floods and droughts, forest fires, hurricanes, and tornadoes
density-dependent factor
a biotic interaction that varies in its effect on population growth, depending on the density of the populations involved. ex. competition or predation
intraspecific competition
a situation in which members of the same population compete for resources
interspecific competition
a situation in which two or more populations compete for limited resources
driving force for evolutionary change
in competing species, individuals that are most _______ from their competitors will be best able to avoid competitive interactions and will therefor obtain the most resources
different
how do producer-consumer and predator-prey relationships put selective pressure on both parties
the more successful predators and consumers drive the natural selection of the produces and prey
example of how the scarcity of a producer or prey species will limit the growth of a consumer or predator species’ population
trees have a direct relationship with birds and beavers
population cycles
alternating periods of large and small population sizes
sinusoidal growth
a wave like oscillating growth patterns that is typical of predator-prey interactions
protective colouration
adaptations that help individuals avoid predation; includes camoflauge, mimicry, and body colouration used as a warning signal
symbiosis
an ecological relationship between two species living in direct contact; includes parasitism, mutualism, and commensalism
parasitism
a symbiotic relationship in which a symbiont lives off and harms the host. ex. insects, viruses, unicellular organisms, various types of worms
parasite-host cycles are similar to predator-prey cycles
mutualism
a type of symbiotic relationship in which both species benefit from the relationship
both partners co-evolve. growth in one population typically spurs growth in the other population
commensalism
a symbiotic relationship in which one partner benefits and the other partner neither benefits nor is harmed
demography
the study of statistics related to human populations, such as population size, density, distribution, movement, births and deaths
factors that allowed humans to increase the carrying capacity of their environment and change from a logistic to exponential growth pattern
- increased food supply by improved agricultural methods and domestication of animals
- breakthroughs in medicine, cured once-fatal illnesses
- better shelter, protection from weather
- food storage capacity improvements
doubling time
the time it takes for a population to double in number
population pyramid
a type of bar graph that shows the age distribution in a population, which demographers use to study a population
shape of a population pyramid is used to predict demographic trends in the population
what do different shapes of population pyramids predict
triangular - predicts a future of explosive growth because a large portion of the population will enter their reproductive years at the same time
rectange - stable
inverted triangle - shrinking
humans have been able to _______ the carrying capacity of Earth, and the population continues to grow exponentially. However, all environments have a ______ and there is _______ to suggest that Earth is no exception
increase, limit, no evidence
ecological footprint
the amount of productive land that is required for each person in a defined area, such as a country, for food, water, transportation, housing, waste management, and other requirements
six major categories of deman
cropland, grazing land, fishing groups, forest land, carbon absorption land, and building area
largest component of carbon footprints for developed countries (ex. Canada and USA)
land for energy production, food production, and forestry
available biocapacity
earth’s carrying capacity for the human population
low-productivity areas such as arid regions and open oceans, are not considered biologically productive areas in this calculation. it is estimated that about 1/4 of Earth’s surface constitutes Earth’s biocapacity
costs of the growing human population and challenges to manage growth and resources
demand for energy, greater need for food, need for adequate waste disposal, decline in biodiversity
the greatest human-produced source of mercury emissions. what dangerous element is found in coal
coal-burning power plants
mercury
how does mercury enter ecosystems
when mercury enters the atmosphere, it quickly enters waterways, either settling directly into lakes and streams, or washing into them after being deposited on land. once in water, certain micro-organisms convert mercury into methylmercury. living organisms easily absorb this highly toxic form of the metal. methylmercury quickly biomagnifies up the food chain to the higher-level consumers, including humans who eat fish and shellfish.
biomagnification
the increase in concentration of a substance, such as methylmercury or DDT, that occurs in a food chain and is not broken down by environmental processes
how does mercury affect ecosystems and organisms
when methylmercury reaches high enough levels in animals, the chemical typically interferes with growth, development, and reproduction. harm to the nervous system may result in abnormal behavior and eventual death. chronic exposure in humans damages the kidneys, liver, and lungs, as well as the immune and nervous systems. in pregnant women, it interferes with the brain development of the fetus. in young children, high levels may interfere with brain development and the ability to learn
how can we reduce the amount of pollutants released into the atmosphere
replacing fossil fuels such as coal and natural gas with renewable forms of energy
where is the need for food the greatest
where population growth and poverty are greatest
deforestation
the cutting, clearing, or removal of trees so land can be used as pastureland or cropland
populations in poverty cut down forests to clear space for growing subsistence crops to feed rapidly growing populations and to make charcoal to sell for fuel to people in urban centres
tropical rainforests are among the most productive ecosystems in the world. however, the soil in this ecosystem is extremely poor. explain why the poor soil does not support life
few nutrients ever reach the soil. instead, the nutrients and water needed by organisms in the rainforest are recycled within these biotic components. in addition, abundant rainfalls in these ecosystems result in erosion in areas that are cleared of trees, especially slopes. subsequently, mudslides can carry both soil and vegetation into waterways
explain how the consequences of soil erosion have been catastrophic for places like Haiti and Madagascar
thousands of tonnes of soil are washed away. poverty in these nations often means people have no choice but to clear land
sustainable
the use of resources, such as food, energy, timber and other items acquired from the environment, at a level that does not exhaust the supply or cause ecological damage
how can deforestation be combatted
planting trees, terracing hills to stop erosion and prevent mudslides and landslides during the rainy season
bycatch
aquatic organisms that are caught unintentionally by fishing gear or nets and often are discarded as waste
how have demands on global fisheries harmed the environment
advances in technology have brought with them destructive fishing techniques that remove nearly all animal life from the sea floor
sources of marine debris
cargo and passenger ships, oil platforms, and runoff from rivers
why is plastic the most dangerous of all the forms of waste found in the sea
takes years to decay
ultimately finds its way into or onto marine organisms
how does the consumption affect organisms (ex. nurdles)
plastic pellets called nurdles are easily consumed by marine life. plastics contain chemicals that mimic estrogen. an overabundance of estrogen has been shown to disrupt the endocrine system of organisms, to lead to the feminization of males, and to cause reproductive problems. plastics also attract and concentrate toxins such as mercury and pesticides
one way to reduce waste
recycling materials and manufacturing and purchasing items that have a long life (as well as having reusable/recyclable components)
biodiversity
encompasses species diversity (the variety of plants, animals and other organisms on Earth), the genetic diversity that exists within each species, and the diversity of ecosystems (ecosystem diversity) to which these species belong
how does biodiversity stabilize ecosystems
making them more resilient to change and degradation
change can be natural disasters such as drought and flood or human-caused events such as oil spills and acid rain
ex. monoculture crops are vulnerable
why is ecosystem stability essential to the survival of our species (examples)
wetland ecosystems filter and purify the water we drink
marine forest ecosystems take up atmospheric carbon dioxide which helps regulate our climate
other ecosystems provide us with materials to build shelters, food resources, and even medicine
habitat loss in deforestation as a threat to biodiversity
organisms lose home and migrate or die
organisms reliant on dead organisms also die
competition in old and new habitat increase and more deaths occur
habitat loss in habitat fragmentation as a threat to biodiversity
roads, dams, water diversions are built and habitats are cut into pieces/fragments
fragments limit interactions among populations, restrict movements of large animals that need large areas to find food and mates, and make it difficult or impossible for migratory species to complete their migrations
habitat loss in habitat degradation as a threat to biodiversity
pollution can completely destroy habitats, and invasive species can out-compete native species to the point of eliminating them from the habitat
overexploitation
the excessive harvesting or killing of a species until it no longer exists or is reduced to a very small population
risks of overexploitation
extinction of a species, which is the disappearance of all members of a species from Earth
reduction of a population below the minimum viable population size, which is the lowest number of individuals that can persist in an environment for a long period of time without the species going extinct
what happens when a population goes below the minimum viable population size
individuals might have trouble finding mates. the population’s genetic diversity will be low and inbreeding will occur, producing weakened or abnormal offspring. in this situation, genetic diversity might be too low for individuals to adapt to changing conditions
what are invasive species and how do they threaten biodiversity
non-native species that relocate to an area and out compete the native species for resources
because invasive species usually do not have predators in their new environments, they reproduce in large numbers
how do pollutants threaten biodiversity
by reducing the number of individuals in a population which can lead to a species extinction ex. methylmercury, DDT
