Topic 6 - Populations And Communities Flashcards
What is a population
A group of organisms of the same species living in a particular area
What are the 4 distinct phases of Population growth
Lag phase
Exponential phase
Stationary phase
Decline phase
What is the Lag Phase in population growth
This is a strange when nutrient assimilation takes place involving the bacteria activating genes and producing the appropriate enzymes to metabolise a particular food substrate
What is the exponential phase in population growth
This is when there is no restriction of growth and bacteria divides exponentially
What is the stationary phase in population growth
This is the stage when food supplies may begin to become limiting so the number of new individuals produced falls
What is the decline phase in population growth
This is when the death rate exceeds the birth rate and the population declines, possibly due to accumulation of waste or nutrient supply running out
What is the biotic potential
The maximum rate of growth as seen in the exponential phase
What is environmental resistance
The restriction by the environment on the population reaching its maximum growth rate and its biotic potential
What are abiotic factors
Factors in the chemical or physical environment and are losselt referred to as non-living
What are biotic factors
The effects of other organisms whether the same or other species
What is the carrying capacity
The maximum number of a population that the ecosystem can support
What are renewable resources
The nutrients that were there at the start of the investigation were not replaced
What is intraspecific competition
Competition between members of the same species
What is interspecific competition
Competition between members of a different species
What are some commons features of a predator-prey graph
The predators peaks and troughs lag behind the preys peaks and troughs
The length of the predator cycle is usually similar to the length of the prey cycle
The number of predators is normally significantly lower than the number of prey individuals
What are r-selected species
Opportunistic Individuals or groups that tend to grow very quickly and increase in population when conditions are ideal
What are k-selected species
Stable populations and the population size usually remains at or close to the carrying capacity of the species
What are some features of an r-selected species
Small body size
Short lived
Reproduce rapidly
Little parental care
Population size variable
Low competitive ability
Not specialised
Inhabit unstable habitats
What are some features of K-selected species
Large body size
Long life cycle
Few offspring
Large amount of parental care
Low dispersal ability
High competitive ability
Highly specialised
Occur in stable habitats
What is a parasite
An organism that lives in or on another organism benefiting from jr and causing it harm over an extended period of time
How do Parasites differ from predators
The parasite lives in or on the host
The parasite causes harm to the host over an extended period of time
The parasite is usually smaller than the host
The parasite seldom kills the host
What is mutualism, and give an example
The interaction where both partners benefits, Lichens between Fungi and green algae
What is a pest species
A species that damages a valuable/ commercial crop species, causing economic damage
What does biological control involve
Deliberately introducing an organism that will target and cause harm to a pest
What are some advantages of effective biological control processes
There is no chemical damage to the environment, reducing bioaccumulation
Biological control targets only the pest species
The develop,end of resistance by the pests is unlikely
Pest resistance is unlikely
Biological control needs little additional action and saves money on the continuing use of pesticides
What are some disadvantages of effective biological control processes
The pest is unlikely to be totally eliminated, which could cause a pest resurgence
It will only work well if the control species can adapt well to the ecosystem
The introduced species may outcompete native species
What is a community
The sum total of all populations in a particular area
What is an ecosystem
The community plus its physical environment
What is succession
The term used to describe the changes over time in ecosystems
when does primary succession occur
On newly formed, barren substrates that have not been previously colonised
What is the first stage of primary succession
The appearance of colonising pioneer species
What increases and decreases and succession develops
Soil depth ,soil fertility and plant biomass increases
Plant diversity initially increases but tends to decrease towards the end
What is the climax community
The stable end of a succession which is in equilibrium with the environment
What is the second stage of succession
Mosses grow in thin soils that develop in rock crevices
What is the third stage of succession
Plants grow deeper in the soil formed by decomposition of earlier pioneer species
What is the fourth stage of succession
Shrubs and small trees develop in deeper soil. Diversity is high as trees do not form a compete canopy
What is the final stage of succession
Soil depth reaches maximum and larger trees begin to outcompete the smaller trees. Diversity drops as few species can survive
What are some common features of primary succession
They are predictable in pattern
The abiotic environment becomes less hostile
The height and biomass of vegetation increases
Communities become increasing complex
Communities in later stages of the succession are usually more stable than in earlier seres
