Unit 6.2 - Populations and communities Flashcards
Populations and communities
Population
Consists of one species in one location at a time. All members are the same species and therefore capable of breeding to produce fertile offspring
Reproductive Isolation
Occurs when there is a barrier which prevents individuals from reproducing. Speciation can only occur if populations of a species are reproductively isolated
Sampling
A method of investigating the abundance and distribution of populations
Random Sampling
Carried out to ensure: Representation - it is important that all individuals in a location can be selected for sampling, Removal of biases, Generalisation - allows scientists to generalise data from samples to a larger habitat
Sampling Error
The difference between an estimated population size and the true population size
Quadrat
A square frame that is randomly placed in an area to be studied to provide a sample
Sessile
not free-moving
Standard Deviation
Used to show how values are spread above and below the mean
Capture-Mark-Release-Recapture
Is a method of estimating the population size of a motile species
Lincoln Index
The formula for this estimated population: M*(N/R)
Carrying Capacity
The maximum population size of a species that can be supported long term in an environment
Density-Dependent Factors
Cause a population’s growth to change due to population density. They tend to be biotic and typically as the population increases, density dependent factors will decrease populations back to carrying capacity
Density-Independent Factors
Factors that limit population growth but are not dependent on population density. Density independent factors are usually abiotic
Population Density
The number of individuals within a given area
Disease
A biotic factor, affecting population density
Natality
The birth rate for a population
Mortality
The death rate of a population
Immigration
New individuals entering a population
Emigration
The individuals leaving a population
Exponential Growth
Is observed in an environment with limited competition for resources
Sigmoid Population Growth Curve
When a species enters a new location, the population typically produces a Sigmoid population growth curve. Featuring, an exponential phase, transitional phase and plateau phase
Intraspecific Relationships
Relationships between members of the same species
Interspecific Relationships
Relationships between members of different species
Community
Is formed by populations of different species living and interacting with each other in an ecosystem
Herbivory
Is the act of eating plants
Predation
Is the act of preying on other animals
Interspecific Competition
Occurs when individuals from different species compete with each other for the same resources
Mutualism
Is a close relationship between the organisms of different species, in which both individuals benefit from the activity of the other
Parasitism
Is a form of symbiosis where one species benefits, but the other species is harmed
Pathogenicity
Occurs when an organism infects another species, causing a disease
Root Nodules
Plants in the legume family, including soybeans, have nodules containing nitrogen-fixing bacteria. Plants require nitrogen compounds, but are unable to synthesise these compounds. These nitrogen fixing bacteria provide the plant with a supply of nitrogen compounds. The bacteria recieves carbohydrates and other organic compounds, produced by photosynthesis, from the plant.
Mycorrhizae
Are formed by a symbiotic relationship between the roots of a plant and a fungus. e.g orchids
Zooxanthellae
Zooxanthellae algae have a mutualistic relationship with coral polyps. The zooxanthellae produce nutrients such as glucose used by the corals, as well as removing wastes and producing oxygen. The coral polyps provide protection and carbon dioxide for the zooxanthellae.
Endemic Species
Native species
Invasive Species
Often replace endemic species by competitive exclusion
Alien Species
Are organisms that have been introduced into an ecosystem, and do not occur there naturally. Alien species become invasive species if they cause harm to the natural ecosystem
Competitive Exclusion
States that no two organisms can occupy the same niche as one will be better adapted for the niche, and will outcompete and exclude the other species from the niche
Hypothesis
A proposed relationship between two or more variables that can be tested by experiment
Test of Association
Tests to determine if there is a relationship between two species or between a species and an abiotic factor in an ecosystem
Chi-Squared Test of Association
Carried to determine if data collected suggests whether two species in an ecosystem are associated with each other
Predator-Prey Cycle
Cycles in which predator and prey populations control each other e.g with Lynxes and snowshoe hares. When prey populations are high, there is a plentiful supply of food for predators and the predator population increases too, however this causes the prey population to decrease which then results in less food supplies and the predator population decreases again. The cycle continues, creating predator-prey cycles
Top-Down Control
Pressures applied at higher trophic levels to control dynamics in an ecosystem. The top predator prevents overpopulation of its prey which has an impact on many species within the ecosystem
Bottom-Up Control
Are resources available to producers, affecting the growth rate of producers. Population growth at higher trophic levels is impacted by the availability of producers.
Allelopathy
Is the release of chemicals by one organism which influences the germination, growth, survival or reproduction of another organism
Antibiotic
Inhibits the growth of fungus, reducing the competition for resources by inhibiting the growth of bacteria near the fungus
