Chapter 5 Population Size and Ecosystems Flashcards
Define population
An interbreeding group of organisms of the same species occupying a particular habitat
Define birth rate
The reproductive capacity of a population; the number of new individuals derived from reproduction per unit time
Define immigration
The movement of individuals into a population of the same species.
Define fugitive species
Species that are poor at competition and rely on a large capacity for reproduction and dispersal to increase their numbers.
Define equilibrium species
Species that control their population by competition within a stable habitat.
What is the pattern of growth shown by equilibrium species?
Sigmoid curve (s-shaped) called one step growth
What are the phases of one-step growth?
Lag phase Log phase Exponential phase Stationary phase Death phase
What happens during the lag phase?
The population has a slow increase. This is because it is a period for adaptation or preparation for growth. In sexually reproducing animals it is the time in which individuals can reach sexual maturity, find a mate and gestate their young.
What happens during the log phase?
Number of individuals increase rapidly. In bacteria, they double per time as they constantly divide.
Why can’t the log phase be maintained indefinitely?
Environmental resistance occurs in which there are limiting factors such as food availability, overcrowding, competition and concentration of waste products.
What happens during the stationary phase?
When the birth rate equals the death rate. The population has reached its maximum size, which is the carrying capacity for that environment.
Define carrying capacity
The maximum number around which a population fluctuates in a given environment.
What happens during the death phase?
When the death rate is greater than the birth rate as a result of environmental resistance. The graph as a negative gradient.
Define abundance
The number of individuals in a species in a given are or volume
What are the ways abundance can be measured?
Capture-mark-recapture experiments
Quadrats
Define distribution
The area or volume in which the organisms of a species are found
How is distribution measured?
Line transects
Define ecosystem
A characteristic community of interdependent species interacting with the abiotic components of their habitat
Give examples of ecosystems
Seas, oceans, arctic tundra, forest, desert
Define habitat
The place in which an organism lives
Define Community
Interacting populations of two or more species in the same habitat at the same time
Define trophic level
Feeding level in which the number of times that energy has transferred between the sun and successive organisms along a food chain
Define biomass
The mass of biological material in living or recently living organisms.
Explain how food chains work?
Green plants, Cyanobacteria, and some protoctista are called producers because they incorporate the suns energy into carbohydrates. Herbivores are primary consumers that digest the carbohydrates from the plants and incorporate the energy into its biomass. Carnivores are secondary and tertiary consumers. As energy is passed along the food chain there is a loss from the food chain at each level.
Define saprobiont and explain their role in the food chain?
A microorganism that obtains it’s food from the dead or decaying remains of other organisms. Therefore, when producers or consumers die, saprobionts incorporate the energy that remains in the organic compounds of which they are made.
How do you calculate photosynthetic efficiency?
PE = quantity of light energy incorporated into product/ quantity of energy falling on the plant x 100
Define gross primary productivity
The rate of production of chemical energy in organic molecules by photosynthesis in a given area and given time, measured in KJ/m^2/yr
Define net primary productivity
Energy in the plants biomass which is available to primary consumers, KJ/m^2/yr
Define primary productivity
The rate at which energy is converted by producers into biomass
Define secondary productivity
The rate at which consumers convert the chemical energy of their food into biomass
Explain how energy is lost as it passes along the food chain
Energy in molecules that are egested (E.G - cellulose in humans)
Energy is lost as heat
Energy remains in molecules in parts of animals that may not be eaten for example, fur, horns and bones
Why do herbivores have a lower conversion efficiency than carnivores?
Herbivores do not eat all the vegetation available to them for example, grazing cattle only eat grass and small herbaceous plants and not roots or woody parts of plants. Carnivores are more efficient at energy conversion because their food is more easily and quickly digested.
Why do warm blooded animals have a lower productivity than cold blooded animals?
Warm blooded animals lose more energy as heat in order to maintain a constant internal body temperature. Cold blooded animals do not have to do this.
How do you calculate efficiency of energy transfer?
Efficiency = energy incorporated into biomass after transfer / energy available before transfer x 100
What are the 3 types of ecological pyramids?
Pyramid of numbers
Pyramid of energy
Pyramid of biomass
What does a pyramid of numbers measure?
The number of species at each trophic level
What does a Pyramid of energy measure?
Energy at each trophic level
What does a pyramid of biomass measure?
The amount of energy incorporated into the macromolecules of animals (biomass) at each trophic level
Define succession
The change in structure and species composition of a community over time
Define climax community
A stable, community that has reached equilibrium with its environment, and no further change occurs.
Define primary succession
The change in structure and species composition of a community over time in an area that has not previously been colonised
Define pioneer species
The first species to colonise a new area in an ecological succession
Outline the seral stages of primary succession in a xerosere
Pioneer species of lichen erode rock. The accumulation of dead organic matter as the lichen and moss die leads to the formation of a primitive soil. Wind-blown spores allow moss to grow and as soil develops, grasses and other small herbaceous plants outcompete the moss. As these plants die the soil becomes thicker with more minerals, allowing shrubs and small trees to grow. The soil continues to deepen and large trees such as oak are established. Once these large trees grow the xerosphere has reached its climax community.
Define secondary succession
The changes in a community following the disturbance or damage to a colonised habitat.
How do humans cause Disclamax in communities?
Deforestation removes a community of large trees
Grazing by sheep and cattle
What factors affect succession?
Migration
Competition
Facilitative relationships (mutualism/commensalism)
How does migration affect succession?
Arrival of spores, seeds and animals is vital for succession to progress. Immigrating non-native species may spread themselves widely altering the community and the soil
How does competition affect succession?
Competition operates at several stages of a succession, 2 species cannot occupy the same niche and whichever species has the competitive advantage will survive and can remain in the community during the stages of succession.
How do facilitative relationships affect succession?
Facilitation in an ecological community provides better resource availability for the species that benefit from mutualism and commensalism
