12. Population Ecology Flashcards
What is Ecology?
Ecology is the scientific study of the interactions between organisms and the environment
These interactions determine distribution of organisms and their abundance
What is a Population?
A population comprises all individuals (organisms) of a given species in a defined area
What is a Community?
A community is a group of populations of different species in a defined area
What is an Ecosystem?
An ecosystem is the community of organisms in an area and the physical factors with which they interact
What is a Biosphere?
The biosphere is the global ecosystem, the sum of all the planet’s ecosystems
Most Inclusive Level vs Least Inclusive Level
- In terms of biological levels of organization, the most inclusive level (which incorporates all living organisms and non-living factors) is the biosphere
- As we move down each level, there is less inclusivity (with the organism or individual representing the least inclusive level)
What is Population Size?
population size (N)
- the total number of individuals
What is Population Density?
population density
- the number of individuals within a specific area or volume
What is Quadrat analysis?
Quadrat analysis is used to quantify immobile organisms and small, slow-moving organisms
– A series of squares (quadrats) of set size are placed in habitat of interest and species within quadrats are identified and recorded
- researchers count number of individuals within boundaries of each one
- Multiple quadrat samples are performed throughout the habitat at several random locations, (which ensures that the numbers
recorded are representative for the habitat overall) - data can be used to estimate the population size and population density within the entire habitat
What counts and doesn’t count in the quadrant?
3 Types of Sampling Distributions
Quadrat Data Formula
What is Mark-release-recapture?
Mark-release-recapture used to quantify mobile organisms
– In mark-release-recapture, a known number of animals are caught, marked in some way, and then released back into the community
– Later, a number of individuals are collected randomly and the number of marked individuals are recorded for estimating actual population size
What are some different marking methods?
(6)
Marking methods depend on species:
– Birds can be banded with a small aluminum ankle bracelet
– Snails can be marked with waterproof paint on their shells
– Butterflies can have labels taped to their wings
– Large mammals fitted with collars
– Amphibians can have nontoxic dyes injected under the skin
– Fish fins can be notched or hole-punched
Equation used in mark-release-recapture
What assumptions are made when using the mark-recapture method to estimate the size of the target animal population? (5)
- animals are randomly dispersed;
- animals are not immigrating or emigrating from the population between the marking and recapture efforts;
- no new animals are born and none have died between the marking and recapture efforts
- marked and unmarked animals have the same chance of being recaptured
- the type of marking used does not influence the animal’s chance of being recaptured or being preyed upon
What is Clumped Distribution? (4)
Clumped distribution is the most common type of dispersion
– Distance between neighbouring individuals is minimized (individuals are clustered)
– Clumped spacing arises from social predisposition to form groups [i.e., for thermoregulation, better foraging cooperative hunting and safety from predators]
– Another reason for clumped spacing is the inability of offspring to independently to move from their habitat (this is seen in juvenile organisms that are immobile and strongly dependent upon parental care)
Examples of Clumped Distribution
(4)
Examples:
- Plants that drop their seeds straight to the ground (i.e., oak trees) and germinate to produce young seedlings very close by
- Animals that live in groups (i.e., avian flocks, wolf packs, schools of fish or herds of elephants)
- Sea stars are often clumped where food is abundant
- Bald eagle’s nest of eaglets being cared for by their mother
What is Random distribution? (4)
Random distribution is the least common type of dispersion
– Distance between neighbouring individuals is unpredictable (no pattern)
– Exhibited by individuals that do not form social groups (they neither attract nor repel one another)
– Occurs in habitats where environmental conditions and resources are consistent (resources are not scarce enough to require territorial spacing or cooperative behaviour)
Examples of Random Distribution
Examples:
- Dandelions and other plants that have wind-dispersed seeds (seeds spread widely and sprout where they happen to fall, as long as the environment is favourable – has enough soil, water, nutrients and light
- Oyster larvae can travel hundreds of kilometres powered by sea currents, which results in their random distribution
What is Uniform distribution?
Uniform distribution is also known as even distribution (less common than clumped but more common than random distribution)
– Distance between neighbouring individuals is evenly spaced
– Common among territorial individuals defending scarce resources or defending breeding territories
– Helps to ensure adequate resources for each individual
Examples of Unifrom Distribution?
(2)
Examples:
- Penguins often exhibit uniform spacing by aggressively defending their territory among their neighbours (this is also seen with iguanas, shorebirds and owls)
- Plants that undergo allelopathy (like creosote bushes and cacti) excrete chemicals that can inhibit the growth and germination of other plants that compete for the same resources
What are Biotic Factors?
Biotic factors =
living components of an ecosystem (such as plants, animals, bacteria, fungi, protists, and more)
What are Abiotic Factors?
Abiotic factors =
non-living or physical components of an ecosystem (such as temperature, water, sunlight, atmosphere, humidity, wind, rocks, soil, pH)
What do Biotic components usually include?
(3)
Producers (autotrophs)
convert the energy from sunlight or inorganic chemical compounds to synthesize organic molecules
Consumers (heterotrophs)
are animals that depend upon producers for food
Decomposers (heterotrophs)
play a critical role in keeping ecosystems healthy
Examples of Producers (2)
Photoautotrophs –
such as plants, use energy from sunlight to make organic compounds (like sugars) out of carbon dioxide in photosynthesis (other examples of photoautotrophs include algae and cyanobacteria)
Chemoautotrophs –
use energy from inorganic sources (i.e., hydrogen sulfide, sulfur, iron, and ammonia) to make organic compounds out of carbon dioxide or similar molecules
Examples of Consumers (3)
Herbivores –
animals that only eat plant material (i.e., deer, rabbits, giraffes, koalas)
Omnivores – animals that eat a variety of food sources which include plants, animals, algae and fungi (i.e., bears, crows, foxes, and humans)
Carnivores – animals that eat other animals (lions, tigers, vultures, eagles and wolves)
What are Decomposers?
What are Detrivores?
Decomposers (heterotrophs) play a critical role in keeping ecosystems healthy
- When they break down dead material and wastes, they release nutrients that can be recycled and used as building blocks by primary producers
- Decomposers (i.e., fungi, cockroaches, wasps, bacteria) break down organic matter from a decaying organism externally whereas detritivores (i.e., earthworms, dung flies, mites, sea stars, millipedes, slugs, woodlice, vultures, crabs, etc.) consume the dead and decomposing organic material created by decomposers to gain nutrients internally
What are Detritivores?
Detritivores are a branch of decomposers
What is Demography?
Demography is the study of vital statistics of a population and how they change over time
Death rates, birth rates and life expectancies are of particular interest to demographers
What is a Life Table?
A life table is an age-specific summary of the survival pattern of a population
It is best made by following the fate of a cohort, a group of individuals of the same age
A survivorship curve is graphic way of representing data in life table
Type 1 Survivorship Curve?
Humans and most primates have a Type I survivorship curve
– Low death rates during early and middle life, then an increase in death rates among older age groups
– Species with Type I curves usually have small numbers of offspring and provide lots of parental care to make sure those offspring survive
Type II survivorship curve?
Many bird species have a Type II survivorship curve
– Death rate is constant over the organism’s
– Organisms with this type of survivorship curve may also have relatively few offspring and provide significant parental care
Type III survivorship curve?
Trees, marine invertebrates, and most fish have a Type III survivorship curve
– High death rates for the young, then a slower death rate for survivors
– Species with this type of curve usually have lots of offspring at once—such as a tree releasing thousands of seeds—but don’t provide much care for the offspring
What is semelparity, or big-bang reproduction?
Species that exhibit semelparity, or big-bang reproduction, reproduce once and die
[such as Pacific salmon, bamboo, and grain crops like wheat]
What is iteroparity, or repeated reproduction?
Species that exhibit iteroparity, or repeated reproduction, produce offspring repeatedly
[such as humans (although people can choose not to have children), all birds, etc.]
General equation for the population growth rate
(change in number of individuals in a population over time):
What is Exponential Growth?
- In exponential growth, population’s growth rate increases over time, in proportion to size of population
– Bacteria grown in lab provide an excellent example of this type of growth - Key concept of exponential growth is that population growth rate (number of organisms added in each generation) increases as population gets larger
- When population size (N) is plotted over time, a J-shaped growth curve is generated
What is Logistic Growth? (3)
Logistic growth is continuous population growth in an environment where resources are limited; it is density-dependent growth
What is “r”?
“r” is known as the intrinsic rate of population growth or per capita population growth rate since it measures whether the population tends to
grow (r>0),
shrink (r<0) or
stays the same (r=0)
o In other words, r is the rate at which the population size changes per individual in the population
o This growth rate is determined by the birth, death, emigration, and migration rates in the population
What is “r_max”?
r”_max” is maximum population growth rate for a particular species under ideal conditions, and it varies from species to species
– For instance, bacteria can reproduce much faster than humans, and would have a higher maximum per capita rate of increase
– Maximum population growth rate for a species, sometimes called its biotic potential, is expressed in following equation:
density-independent growth
Exponential growth
density-dependent growth
Logistic growth
Logistic Growth Shape
- Logistic growth is a more realistic model of population growth than exponential growth
- There are 3 different sections to an S-shaped curve:
– Initially, growth is exponential because there are few individuals and ample resources available
– As resources become limited, growth rate decreases
– Finally, the growth rate levels off at the carrying capacity of the environment, with little change in population number over time
What is Carrying Capacity?
maximum population size a particular environment can support is called the carrying capacity, or K
K measures population size which produces enough offspring to just replace itself
– NOTE: important to recognize that K varies among species and populations, and changes over time since conditions are better in some seasons and years than in others
Density-independent factors
o Alter birth rates and death rates irrespective of number of individuals in population
o Involve changes in abiotic environment
– variation in weather patterns, or catastrophic events such as cold snaps, hurricanes, volcanic eruptions or drought
Density-dependent factors (5)
Changes in intensity as a function of population size, and they are usually biotic
What is r/K selection theory?
r/K selection theory relates to the selection of combinations of traits in an organism that trade-off between quantity and quality of offspring
What is an r-selected species? (3)
An r-selected species is one that has:
- high rates of fecundity (measure of reproductive rate)
- low levels of parental investment in the young, and
- high rates of mortality before individuals reach sexual maturity
(evolution favors productivity in r-selected species)
What is a K-selected species? (3)
A K-selected species has:
- low rates of fecundity,
- high levels of parental investment in the young, and
- low rates of mortality as individuals sexually mature (evolution favors efficiency in the conversion of more resources into fewer offspring)
equilibrial … such as birds, humans, primates, horses, tortoises, elephants and sequoia trees)
r-selected and k-selected species exam
r-selected and k-selected species differences
