Population Ecology Flashcards
What is a species
A group of organisms with similar characteristics, which are able to reproduce fertile offspring
What is a population
A group of organisms from a single species that are located in an area in which they can mix and breed
What is a community
All the populations of living organisms living in a particular area
What is a habitat
The particular environment in which an animal or plant species normally occurs
What is an environment
The external factors, both biotic and abiotic, which surround an organism and influence its development and survival
What is an ecosystem
The interactions between biotic factors (animal and plant communities) and abiotic factors in an area
What are the 4 population parameters
- Natality - birth rate of a population (counted as number of births per one thousand in one year)
- Mortality - death rate of a population (counted as number of deaths per one thousand in one year)
- Immigration - one way movement of organisms into an area
- Emigration - one way movement of organisms out of an area
Which direct technique can be used to determine population size
Census - direct counting of individuals
Suitable for large, clearly visible and slow moving/sessile organisms such as elephant and rhino
Census methods:
Direct contact counting
Direct counting from vehicle or helicopter
Direct counting from an aerial photograph
Which indirect techniques are used for determining population size
Only part of th population is counted and calculations are made:
Mark-recapture
Quadrat technique
How does quadrat technique work
Quadrat = metal/ wooden square of known size
Quadrat placed randomly within an area (all individuals of the population will have equal and independent chance of being included)
Organisms inside each Quadrat are counted
Average is calculated
Population is estimated according to the formula:
P = average no. Of individuals per Quadrat x surface area/surface area of Quadrat
What are the requirements for Quadrat technique
Quadrat should be placed randomly
Quadrat should be the same size and shape
More than one Quadrat should be used
If average of individuals has a decimal, always round down
How does mark-recapture technique work
Area to be counted is decided upon , preferably a closed system
1st sample of animals are caught and marked
The marked individuals are given time to mix freely with the rest of the population
After enough time has passed a second sample is caught
Individuals second sample are counted and individuals marked in the second sample are also counted
Population is estimated using formula:
P = marked individuals in sample 1 x total number of individuals in sample 2
———————————————————————————————————
Total no. Of markedly individuals in sample 2
What are the requirements for the use of the mark-recapture technique
Markers should not harm organisms or interfere with their ability to mix freely with other individuals
Markers should be clearly visible for duration of the investigation
Time between capturing sample 1 and 2 should be long enough for individuals to mix freely but not too long that there are deaths and births that affect the estimate
Population must be closed
What are some trapping and marking techniques that can be used for mark-recapture technique
Live trap
Mist net
Ear tag
Painting bird with dye
Animal hide marked with hot-brand/iron
Toe clipping
Rings around foot
What are the 2 types of population growth forms
Exponential growth - J shape
Logistic growth - S shape
Why does the exponential growth graph has its shape
Population growth is slow at first because there are few organisms and they need time to adapt to their environment
There’s a sharp increase in population with cause cause a steep graph
The increase will not happen indefinitely, something in environment will affect the population (environmental resistance)
What causes the shape of the logistic growth graph
Starts the same as exponential growth graph because organisms are few and adapting followed by sharp increase in population growth
Factors in environment slow down the rate of population growth = curve levels off and numbers stabilise
Population will stabilise at the carrying capacity
Stable population - fluctuates just above and below carrying capacity
Carrying capacity can get exceeded by a large margin causing severe shortage of resources = more deaths, less births and dropping population
When environment gets damaged by overpopulation, carrying capacity can drop e.g: overgrazing
4 phases causing shape of graph:
1. Lag phase - organisms need time to adapt, to sexually mature, to find mates and gestation/incubation period
2. Exponential phase
3. Deceleration phase
4. Stationary/equilibrium phase
What is environmental resistance and what creates it
Environmental resistance: the slowing effect of the population growth rate by the environment
Food shortage
Water shortage
Space shortage/ lack of territory
Light shortage
Accumulation of toxins
What are density dependent factors
DD factors: environmental factors that only limit population numbers at high population densities
Examples
Availability of Food
Availability Space
Presence and spread of Disease
Availability of Shelter
Waste accumulation
What are density independent factors
Environmental factors which affect population numbers equally whether population numbers are high or low
Examples
Extreme changes in temperature
Drought
Flood
Fire and other natural disasters
What is carrying capacity
The maximum population size of biological species that can be sustained in that specific environment
What are the types of interaction found in the environment
Predation
Competition
Mutualism
Commensalism
Parasitism
What are the types of interaction found in the environment
Predation
Competition
Mutualism
Commensalism
Parasitism
What is predation
Feeding interaction in which predator hunts, kills and eats its prey
Predators well adapted to catch prey (camouflage, speed, agility ) and prey well adapted to avoid predators (speed, camouflage, agility)
What causes the shape and pattern of a predator prey graph
Predator graph always shadows prey graph
Prey always reaches higher populations peaks than predators
Because:
As prey number increase predators increase because there is more food
More numbers cause prey numbers to drop and then predator numbers drop because of decrease in foodless predators allows prey numbers to increase again
Pattern repeats
What is ecological niche
Ecological niche: Each organism’s specific role to play in the community (and in its role it needs specific environmental conditions and resources in order to survive and reproduce)
What is competition
Interaction between organisms that occurs when two or more individuals compete for the same resources
What is the difference between introspective snd interspecific competition
Intraspecific: competing individuals are of the same species and it always happens, particularly when population numbers are high
Interspecific: two similar species have the same niches that overlap e.g: vultures and hyenas eat dead carcasses
What is resource partitioning and what is an example of it
Resource partitioning: ability for two competing species to co-exist in the same environment
Example 1:
Vulture and hyena both feed on dead carcasses but hyena can also kill their own and vultures are good at locating the carcasses by flying and good eyesight. They are able to do-exist without aggressively competing
Example 2:
Galapagos finches have different beak shapes and sizes to allow them to eat specific types of seeds, so several species of these finches can co-exist without competing for the same type of seed
This is also an example of character displacement (adaptations that take place to eliminate competition)
What is an example of resource partitioning in plants
Stratification to share light
Plants needing most light grow fast and tall to get above all the other trees = canopy tress
Trees and plants needing less light will grow under them = shorter tress and shrubs
Mosses and ferns grow below everything completely in shade
What is competitive exclusion
When two species have identical niches, they cannot co-exist
E.g bushbuck and Nyala - when nyala is introduced in a habitat the bushbuck eventually die out
What is ecological succession
The sequence of communities, where ie community replaces another over time, resulting in long term changes in the ecosystem
What is the difference between pioneer commit/pioneers and climax community
Pioneers (Mosses, lichens, grasses) are the first organisms that become established and they change the environment and make it suitable for complex organisms
Climax community Is the stable ecosystem that develops after changes have occurred in the environment and it has become complex
What is the order of colonial succession in plants
Colonisers - lichens and mosses
Pioneers - grasses
Herbaceous plants - weeds
Shrub - shrubs and bushes
Climax trees - trees
What is primary succession
Occurs when organisms settle in a habitat where there was previously no life
Usually in areas where there was no soil (sand, lava flows, rock)
What is secondary succession
Occurs when organisms settle in a habitat which has been disrupted by human activities or natural disasters such as a fire
Faster than primary succession because soil is already present and nutrients and seeds from previous growth
What is social organisation and what are three types of social organisation found in ecosystems
Social organisation: individuals in some species working together in order to increase their chances of survival
Examples:
Herds as a predator avoiding strategy
Packs as a successful hunting strategy
Division of tasks
What are examples of herds that are socially organised to avoid predators
Large herbivores graze in herds
Many eyes and ears = detect predators easily
Herds can scatter when there is a predator to confuse it
Zebra run as a herd and their stripes create a confusing pattern
Elephant and buffalo stand their ground and protect young ones in the middle
What are examples of packs that are socially organised to hunt successfully
Wild dogs, hyenas and lions hunt in packs = co-operative hunting
Advantages: higher success rate
Can tackle larger prey
Females with youngsters do not have to hunt but can take care of their offspring = reduces infant mortality
What is an example of organisms that socially organise themselves to divide tasks
Eusocial animals: animals in which different species have particular roles or tasks
Eusocial animals have groups/castes that perform specific functions in their colonies
Examples of functions: finding food, caring for young, defence
There is a queen who is the only fertile female and produces all the eggs
Examples of eusocial animals: bees, ants, termites and wasps
What are the reasons for the exponential growth in human population
Developments in medicine, including treatments and vaccinations
Increases in agricultural productivity including mechanisation, disease resistant crops, fertilisers
Better houses because of Industrial Revolution
Increased understanding of how diet affects our health
=
Increased fertility
Decreased mortality
Increased longevity
What is ecological footprint
The human demands placed on the environment
What does ecological footprint measure
Amount of biologically productive land and water there is to regenerate the resources that humans use and to detoxify the waste that humans produce
What is bio capacity
Amount of land and water available to provide resources and absorb waste
What is ecological overshoot
Phenomenon whereby more resources and waste are created than what the earth can supply
What are consequences of ecological overshoot
Collapse of fish stocks
Decreased forest covering
Depletion of freshwater resources
Excessive pollution
Food insecurity
What is an example of biologically productive land
Arable land
Grazing
Forests
Fossil fuel/mining land
Fishing waters
Built-up areas
