Unit 1 Population Dynamics Flashcards
3 factors that influnce population GROWTH
- social, economic, environment
population size for a given species that a specific environment can sustain indefinitely
carrying capacity
examples of INvoluntary regulations of human population growth
famine, disease or war
examples of voluntary regulations of human population growth
(birth control, abstinence, delayed marriage)
measure of person’s daily demands on an ecosystem [Amount of biologically productive area of earth (land and sea) needed to produce resource a person consumes + area needed to absorb and treat resulting waste]
Ecological footprint
gha
Global Hectares (gha)
represents biological productivity on one average hectare.
average amount of gha a person needs to meet their needs
2.1 gha
4 ways to reduce eco footprint
Eat less red meat
Take public transit, fuel efficient car
Reduce electricity use
Buy fresh locally produced food instea of packaged imported food
Populations grow and shrink because…
of difference in birth and mortality rains
demographic transition
When a population moves from growth, stability or decline
8 Impacts of the Industrial Revolution on population
- Begin in mid 1700s
- New machines and factories made goods fast+cheap than before
- Migration from farms to city = urbanization
- Higher standard of living+low mortality rates = more people
- More food could be harvested due to modernization in agriculture equipment and fertilization, requiring same amount of land and employing fewer people
- Sanitation, public and health is advanced leading to dramatic reduction in mortality rate
- Traditionally birth rates were high because of farming culture and child being viewed as an insurance policy, this caused a demographic transition where brith rates were higher than mortality rates
- Developing countries typically did not advance til 1900s, ex. The Bengal famine of 1943 in India killed 4 million people, causing India to import food.
What was the Green Revolution?
- Began in 1960s where agriculture and food production improved
- Norman Borlaugh bred new varieties of wheat and rice that produced higher yields
- These new crops combined with synthetic fertilizers, mechanized irrigation and petroleum bases herbicides and pesticides cause food production to skyrocket
What are 5 factors that can see a trend in reduced family size?
- Wide spread education
- Social advancement of women
- Urbanization
- Economic opportunity
- Low risk of infant mortality
3 Main Environmental Consequences of Human Population Growth
- Pollution (constant irrigation caused fields to be to salty, new chemicals)
- Climate change (fossil fuel use releases CO2 trapping heat close to the earth raising the temperatures)
- Over-consumptions and habitat loss (over consuming removes for other animals, less nutrients in soil, more waste)
define ‘Tragedy of Commons”
- Phrase from ecologist Garrett Hardin in 1968 on cattle grazing
- Commons is a shared field for grazing cattle that is open to everyone, if you try to conserve the grass your competitor will use the resource by using more cattle. So it doesnt pay to conserve the grass. It’s doomed to be over-exploited because everyone feels they have no choice
- Just like ocean fisheries, no one benefits from conserving them
which federal department in canada is responsible for foreign aid?
Canada’s Global Affairs Department
Population
group of individual organisms of the same species that live together in the same geographic area
Population density
how many individuals in a given area, # of individuals per unit area
ex: (26/km2)
Formula:
D (density) = Total number of individuals (N) // Space occupied by Individuals (s)
Ecological space
size of area that is usable by a species
Ecological Density (DEsubscript)
= Total number of individuals (N) // Amount of suitable habitat available for the species (Ecological space available/SEsubscript)
Population dispersion
= how individuals are distributes over the area
patterns of dispersion is also known as
spatial distribution
3 Main Patterns of Dispersion + and how it presents
Clumped dispersion = when organisms group together in an area (for protection, exploitation of resource, asexual reproduction etc.)
Uniform dispersion = equal spacing of individuals across an area (guarding resources for nesting or feeding)
Random dispersion = when individuals are scattered randomly over an area (when individuals are not affected by each other)
2 most common population sampling methods
- Quadrat Sampling
- Mark and Recapture Sampling
When is quadrat sampling not ideal to measure a population
- If sampled area aren’t representative of area
- Organism are heavily clumped dispersion
if you’re taking a quadrat sample of a milkweed population, and you have 10 quadrats, with 21 milkweeds counted. How would you calculate the average count per quadrat? What would it be for this sampling?
Quadrat Sampling
- used for counting abundant organisms that do not move and can be easily scene
- counts are done within small patches of an area and are chosen at random
If you have an average count per quadrat of 2.1 milkweeds per quadrat, and each quadrat was a squared metre each, explain how you’d solve for the population density for this quadrat sampling and the answer.
if a quadrat sampling reveals that the population density for milkweeds is about 2.1 per squared metres, and the rest of the area sampled is suitiable habitat for milkweeds, it’s average ecological density would be
2.1 per squared metre
if a field of milkweeds is sampled using the quadrat method, and the ecological density was found to be 2.1 individuals per squared metre, and the field sampled was 100 squared metres, what would the estimated population size be and what is the formula used?
when is mark and recapture sampling used?
when organisms move around or arent easily seen
what is the population formula for mark and recapture?`
(Total # of Marked (M)) X (Size of second sample (n)) // # of marked recaptures (m)
Mn / m
what are some drawbacks to the mark and recapture method?
- this method assumes that marked and unmarked individuals between the first capture and second does not change, so no immigration or emigration or short time between captures is needed for more accuracy
- Marked individuals have same chance of getting caught in second sample as any of the unmarked ones, marking should not affect their survival or their chance of being recaptured
Fecundity
number of offspring an individual can produce over its lifetime
what happens if a higher percentage of the population is past the fertility age?
population decrease
area with a particular set of feature defined by 2 characteristics abiotic (physical) and biotic (biological)
habitat
7 impacts of organisms moving from different regions to another
Impact to organism
Impact to natural environment
Feeding relationships in new environment
Consequence to human population
Impact on abiotic components
Impact on biotic components
Impact on human population
4 factors of population size
- New individuals added through births (natality) [b]
- Individuals moving into a population (immigration) [i]
- Individuals moving out of a population (emigration) [e]
- Loss through death (mortality) [d]
2 ways of describing Population
Closed Population = not changed be I or E, separated from other populations by distance or barriers
(no immigration or emigration)
Open Population = changed by I or E, no barrier between moving in and out of the population
(immigration or emigration occurs)
What is the formula to calculate net population change
(b+i) - (d+e)
(natality + immigration) subtract (death + emigration)
population dynamics are the result of which 2 types of factors
- Internal factors (eg reproductive ability)
- External factors (eg weather, food supply, predation and disease)
Population ecology
area of biology that studies how populations change overtime in relation to their environment and other species
3 Fundamental Population Growth models
- geometric growth model (constant growth)
- exponential growth model (J shaped curce
- logistic growth model (s-shape, 3 phase of growth)
Explain Geometric Growth Model + it’s formula
- happens in population when birth and death rates are constant (say when they can breed only a certain amount of times per year)
Fixed Growth Rate = (lambda) = population size on a particular day N (t+1) // population size on a particular day N (t)
^^^ ƛ = N(t+1)/N(t) or ƛ = N(t+1)/N(t)
where N is population and t is time
Formula for pop. size at any time
= N(t+1) = N(t)*ƛ^t
Explain Exponential Growth Model + it’s formula
- happens in population when population can increase anytime, causing population to grow continuously and exponentially (like bacteria)
Equation to determine exponential growth at a particular time: dN/dt = rN
Where
N = pop. size
r = growth rate per individual
rN = instantaneous growth rate, how much pop. size is changing at any particular instant in time
Biotic potential
Pop growth that could grow under ideal conditions for an organism
if you have 8000 algae in a pond that is growing at a rate of 0.25 per day, calculate the rN?
So rN would equal the population divided by the growth rate per individual, which would be 2000
Explain Logistic Growth Model + it’s formula
When populations face limits on their growth, the growth curve changes - logistic growth model describes this pattern more similar to what happens in a natural population.
Results in a more sigmoid curve/s-shape. The logistic growth model assumes resources stays constant.
Expressed as:
dN/dt = rN x (K-N)/K
N is population size at time t
r is growth rate per individual
K is carrying capacity
What is K and what it is determined by
Carrying Capacity - determined by density dependent factors and density independent factors
Density-dependent factors + 7 types
Internal factors influence by the density of the population
- Predator Focus
- Resource availability (feeding and breeding territories)
- Aggression (animals can change behaviour in higher density)
- Emigration (leaving population due to density)
- Waste accumulation (fecal matter and urine that can pollute)
- Disease (spread of disease and parasites more quickly)
- Stress (increases in stress levels, leading to weakened immune systems and other health problem)
Density-dependent factors for plants
Amount of Sunlight, water, and soil, and how many other plants are competing for the land
Density-independent factors
external factors not influenced by the density of the population
Ex: storms, pesticide (typically natural disasters and human activity)
Population cycles + 2 main factors that drive the cycle
dramatic increases and decreases over a regular time period to population
- Food supply
- Predation
3 Phases of Population Cycles
Increasing phase: when density and population is low, more to eat, higher fecundity, more production of offspring, number of predators may be low or may switch to other prey
Peak phase: when the numbers of population increases rapidly this is typically due to abundance of food and low predation, this leads to a peak phase as their density increases and can cause increase in predator population
Decline phase: once a population hits peak abundance, the numbers fall quickly due to lack of food and higher predation, as their decline begins so will the predators, restarting the cycle
A survivorship curve
graph that measures the proportion of individuals in a given
species that are alive at different ages.
type I survivorship curve
-Individuals that have high probability of surviving
through early and middle life
- But have rapid decline in the number of individuals
surviving into late life
-means most individuals will make it to
adulthood but the proportion surviving into old age is greatly decreased.
-A type I
survivorship curve is plotted as a convex curve on a graph.
type II survivorship curve
-Shows a roughly constant mortality rate for the species
through its entire life.
-individual’s chance of dying is independent of
their age.
-Type II survivorship curves are plotted as a diagonal line going downward on
a graph.
type III survivorship curve
- depicts species where few individuals will live to adulthood
and die as they get older because the greatest mortality for these individuals is
experienced early in life. - This type of survivorship curve is drawn as a concave curve on
a graph
explain the three survivorship curves, examples of an animal from each, and shape of the curve
Interactions among organisms can be broadly divided into two groups
- Interactions between two organisms (or species)
- Community-level interactions
Communities
= combined interactions of different species together in an area
Ecosystems
groups of communities interacting together
different levels of organism relationships
Individual > population > community > ecosystems
Ecological Niche
= how an organism uses it habitat and resources within it
Competitive relationships occur when:
- 2 or more organisms are using the same set of resources in the same area and both are disadvantage
- The interaction results in a negative outcome for each organisms
Competition can be defined as:
Interspecific: between members of different species
Intraspecific: among members of the same species
Interference competition: direct interaction with each other over access to resource (lions fighting over a kill)
Exploitative competition: indirection competition (one organism eats all fruit off a tree)
Fundamental niche
entire niche an organisms is capable of using based on its physiological requirements
Realized niche
actual niche an organism occupies based on local competitive conditions
Gause principle of competitive exclusion
when two species share similar (or niche) requirements, and resource(s) are limited they cant exist in the same community very long. One will eventually out-compete the other, resulting in the disappearance of the loser.
Resource partitioning
when species share the same area and each species specializing in harvesting one particular subset of the resource
-Ex: Different species of Anolis lizards share the same tree, and each species uses specific sections of the tree, splitting the niche of the whole tree into parts.
Predation
when a predator feeds on its prey causing immediate death of the prey; major force of shaping community structure
- may actively hunt or sit and wait
Three main types of defence for prey:
Morphological defence = involves the shape or structure of an organisms (e.g thorns, spikes, shells)
Chemical defence = chemicals that reduce predation (e.g. skunks, poison ivy, poisons, bad taste with milkweed)
Protective Colouration = use of colour
2 Types of Protective Colouration
Cryptic colouration or camouflage: to hide, not be noticed, ex: insects, lizards
Aposematic colouration: to warn predators they are not good to eat (bright red, yellow, or blue)
Symbiosis
two species live closely together and interact in ways that benefit at least one of the species
3 Main forms of Symbiotic Relationships:
Mutualism, Commensalism, Parasitism
mutualism
both participating species benefit from living closely together , ex: plants and pollinators, gut bacteria and humans
Commensalism
when one species benefits while other species does not yet is unharmed ex: clown fish and anemone
Parasitism
broad category which describes interspecific interaction where one species benefit at the expense of another
three ways Parasitic relationships can be categorized by
Relative size of the parasite to its host (microparasites, macroparasites)
Where the parasites live outside of the host (ectoparasites, endoparasites)
Where They they parasitize behaviours of the host (social parasitism)
Microparasites
microscopic in size
Macroparasites
visible to the macroparasites
Social parasitism
= does not involve a parasite consuming resources from its host body, but focuses on manipulate the social behaviour of the host ex: brood parasitism because the bird manipulates into raising its offspring or brood
Two main categories of community-level interactions
Trophic levels = energy-flow hierarchies of species based on what they eat
Food webs = complex networks of feeding relationships networks; connections among species
Linear feeding relationships through the trophic levels
food chains
when food chains are cross-linked to other food chains
food webs
