Population Ecology (25 marks) Flashcards
Define the term Ecology.
The study of the mutual interaction among living organisms and between living organisms and the environment in which they live.
What is Population Ecology?
The part of ecology that focuses on the factors that influence the population size:
- Growth rate
- Growth forms
- Distribution of individuals inside a population.
Define the term Species.
A group of living organisms with similar characteristics, which produce fertile offspring.
Define the term Population.
A group of organisms of the same species that are found in a particular area at the same time and can interbreed freely.
E.g. The population of giraffes in the Kruger National Park.
Define the term Community.
A group of different populations or species in a particular area.
E.g. The lion, rhino & zebra populations at KNP.
Define the term Ecosystem.
Units of biotic communities interacting with each other and the abiotic factors in a particular area.
Define the term Environment.
The external biotic and abiotic factors surrounding an organism and influencing its development and survival.
Define the term Habitat.
The specific environment in which a plant or animal species normally occurs.
Define the term Population Size.
The total number of individuals in a population.
Define the term Population Density.
The number of individuals of a population per unit area.
E.g. 10 sheep per hectare.
What are Population Parameters?
Name them. (4)
Population parameters are the factors that influence population size.
- Natality
- Mortality
- Immigration
- Emigration
Define the term Natality.
The birth rate of a population that is usually expressed as the number of live births per 1000 individuals per year.
Define the term Mortality.
The death rate of a population, usually expressed as the number of deaths per 1000 individuals per year.
Define the term Immigration.
The one-way movement of organisms INTO an area where they become established.
Define the term Emigration.
The one-way movement of organisms OUT OF an area
to become established.
Define the term Closed Population.
A population where immigration and Emigration do not occur.
Therefore Natality and Mortality are the only parameters that affect the population size.
E.g. Fish in a pond.
Define the term Meta Population.
Smaller populations spatially separated within an environment with SOME immigration and emigration taking place.
What is the difference between DIRECT data collection techniques and INDIRECT data collection techniques?
Direct techniques involve the total count of all the individuals in a population, whilst
Indirect techniques only involve counting part of a population and using statistical calculations to estimate the total population size from the partial count.
Name the DIRECT techniques for determining population size.
- Census (in a human population)
- Counting (e.g. animals in a nature reserve using a helicopter)
- Aerial photographs of groups of animals (a penguin colony)
Name the INDIRECT techniques for determining population size.
- Mark-recapture method (also known as Petersen’s method).
- Quadrat method.
How can you ensure VALIDITY of the Mark-Recapture method?
- Marking methods should not HARM the organism.
- Marks should be CLEARLY VISIBLE throughout the entire investigation.
- Markings should NOT affect the organism’s BEHAVIOR or MOVEMENT.
- SUFFICIENT TIME should be given FOR the MIXING of the 1st sample with the rest of the population BEFORE A 2ND SAMPLE IS CAPTURED.
- CLOSED POPULATION
- SHORT DURATION between 1st sampling and second sampling to ENSURE NO DEATHS OR BIRTHS occur.
How can you ensure RELIABILITY of the Quadrat method?
- The exact number of organisms in each quadrat sampling must be counted (including zeros).
- The surface area of the quad must be known.
- The surface area of the total demarcated area of the population must be known.
- The quad needs to be placed randomly in the demarcated area.
- Not reliable for clumped populations.
How does Geometric/Exponential Growth occur?
When population figures increase rapidly due to ideal or optimal environmental conditions.
What are Population Growth Forms?
Name the 2 basic ones.
Population growth forms are the distinctive growth patterns of a population.
- Geometric/Exponential (J-shaped) growth form.
- Logistic (S-shaped/sigmoid) growth form.
How does Logistic Growth occur?
When a young population consisting of only a few individuals is locate on an area with sufficient resources and little predation.
The limiting factors transform or extend the J-shaped curve into an S-shape.
Define the term Limiting Factors.
Factors that prevent the unlimited growth in a population that would exceed its maximum growth rate.
List 7 limiting factors.
- Shortage of food and water.
- Shortage of living space.
- Shortage of shelter.
- Predation.
- Diseases and Parasitism.
- Accumulation of Toxins
- Uninhabitable Temperatures.
Define the term Environmental Resistance.
All the limiting factors of a particular population taking effect.
Define the term Carrying Capacity.
The maximum number of individuals that an environment can sustain.
Define the term Migration.
When a population moves from its original habitat and returns later, usually due to food availability.
Density Dependent Factors VS Density Independent Factors.
Density Dependent: Factors that TAKE EFFECT when the population size or density increases. The LARGER the POPULATION, the GREATER the EFFECT of these factors.
- Shortage of food & water (high competition reduces natality).
- Shortage of living space (stress reduces natality rate).
- Shortage of shelter (exposed adverse weather n predation).
- Predation.
- Accumulation of waste and toxins.
- Disease and parasitism.
Density Independent: Factors that LIMIT the size of a population REGARDLESS of the population’s DENSITY.
- Extreme temperature changes.
- Natural disasters.
^ Usually cause a DRASTIC DECLINE in population
Define the term Culling.
The selective killing of wild animals when their numbers exceed the carrying capacity of their habitat.
What is SANParks?
South African National Parks.
Name Human Intervention Methods for Regulating the Population Sizes of Animals
- Culling
- Relocation
- Trans-frontier park creation
- Birth control & Sterilization
What is a Trans-frontier Park?
A national park connecting more than one country that was previously isolated by fences that opens up migration routes for animals.
What is a Trophic Level.
The position that a living organism occupies in the food chain.
Briefly describe each Trophic Level (Producer/Primary/Secondary/Tertiary/Decomposer)
- Producers: •Green plants that are able to photosynthesise and produce their own food.
- Primary Consumers: •Herbivores that rely fully on plant material.
•Omnivores that rely partially on plant material. - Secondary Consumers: •Carnivores (feed on primary consumers).
•Omnivores (feeding on animal material).
•Scavengers (feeding on the remains of dead organisms) - Tertiary Consumers: •Carnivores that feed on secondary consumers.
- Decomposers: •Bacteria and Fungi (saprophytes) that feed on dead organic material and break down organic compounds into simple, inorganic substances that are released into the soil.
What are the 5 types of interaction that occur in communities?
- Predation
- Competition
- Parasitism
- Commensalism
- Mutualism
Define the term Predation.
Predation is a feeding interaction where one organism, the predator, hunts, kills and eats another organism, the prey.
What qualities do PREDATORS have that make them well-adapted to hunt to catch their prey?
\+ Speed \+ Agility \+ Camouflage \+ Sharp teeth and claws \+ Intensified sense of smell and sight
What qualities do PREY have that make them well-adapted to escape predators?
- Herding
- Ability to secrete poisonous substances
- Warning colouration
- Camouflage
