U1T4 - Keywords (1) Flashcards
Populations + Communities
Population
Group of organisms of same species living in particular habitat.
Lag Phase
Pop nums remain relatively constant or decline/slow increase in nums. Nutrient assimilation + reproduction.
Exponential/Log Phase
Pop nums increase by same factor each time unit. Each new member reproduces so rapid growth as low competition as sufficient resources + little waste. Increase by intrinsic rate of natural increase (r) as pop exhibits biotic potential.
Stationary Phase
Increased pop numbers result in environmental resistance due to waste accumulation, lack resources + increased comp. Reduced birth rate + increased death rate so pop stays constant. Reaches carrying capacity (k). Most pops stay at this stage.
Decline Phase
Lack resources + increase in toxic waste means birth rate 0 + high death rate. Steep decline/crash in pop nums.
Biotic Potential
Max growth/repro rate of pop under optimum conditions.
Carrying Capacity
Max pop size that can be supported by available resources. Max num organisms ecosystem can support.
Intrinsic Rate of Natural Increase
The rate at which a population increases in size if there are no density-dependent forces regulating the population. Births - deaths per generation time.
Environmental Resistance
Sum of environmental factors which restrict biotic potential of population + limit increase.
Renewable Resource
Resource which can be used repeatedly + replaced naturally.
Non-renewable Resource
Resource that doesn’t renew itself at sufficient rate for sustainable economic extraction in human time-frames.
Detritivores
An animal which feeds on dead organic material.
Survivorship Curve
Shows % of individuals surviving over a year/number of years.
R + K Selection Theory
Relates to selection of traits which promote success in certain environments + originates from work on island biogeography by MacArthur + Wilson. Selective pressures are hypothesised to drive evolution in r or k directions.
R Selected Species
Grow v. quickly as individual, pop size increases rapidly under ideal conditions, numbers decline rapidly in less favourable conditions, emphasis on reproduction + colonisation, less parental involvement, small, short life, high dispersal, not competitive, not specialised so adaptable, unstable habitats + high fecundity.
K Selected Species
Stable pops, large, long life, more specialised so less resistant to environment change, stable habitats, pop close to carrying capacity, emphasis on survival + dominance, not colonisation, successful competition, more parental involvement, low fecundity, less able to migrate so more likely to become extinct.
High/Low Fecundity
Many/Few Offspring at once.
Intraspecific Competition
Competition between members of the same species. Becomes more severe as pop increases + resources become limited.
Interspecific Competition
Competition between members of diff species’. Success of 1 species relates to adaptations of each species in current conditions.
Competitive Exclusion Principle
Situation where, due to severity of competition for resources, 1 species is eliminated. Only occurs when overlap between niches as 2 species’ can’t occupy same niche.
Boom + Bust Population Growth
Seen in R-Selected Species’. Emphasis on reproduction + colonisation, rather than survival. High birth rate in optimum conditions but when conditions less favourable, numbers decrease rapidly.
Grazing
When a herbivore grazes on grass. Herbivore benefits whilst grass loses as it loses photosynthetic ability as leaves are eaten.
Parasitism
Organisms which live on or in host organisms feed upon or within it, benefiting whilst the host suffers, ultimately ending in host death (not always but often)
Predator/Prey Relationship
Predator gains food whilst prey suffers. These relationships lead to oscillating growth curves with peaks and lows. With more prey, numbers increase so prey decreases and numbers decrease. Predator + prey peaks and lows are similar lengths but predator lag behind prey in peaks + troughs, depending on reproduction time. Predators usually lower than prey. e.g. Snowshoe hare + Canadian Lynx
Mutualism
Interaction where both partners benefit. Often, eventually, 1 species can’t survive on its own.
Pest
Species that competes with/adversely affects a valuable/commercial pop of crop species/animals causing economic damage.
Biological Control
The use of natural enemies to reduce numbers in pops of pests, without the risks of chemicals. Aims to reduce numbers to where they don’t cause economic damage rather than eradicate. Deliberately introduce predator species to target pest.
Antagonists
Biological control agents of plant diseases. e.g. herbivores + plant pathogens.
Pathogens
Disease causing organisms which kill/debilitate host + are relatively specific e.g. bacteria, fungi + viruses.
Pest Resurgence
Numbers of pest dramatically increase due to elimination of natural predator by broad spectrum pesticide.
Community
Biotic component of ecosystem which involves autotrophic + heterotrophic interactions. All populations of different species’ living in same place at same time + interact with each other.
Ecosystem
Natural unit consisting of all plants, animals + micro organisms (biotic factors) in area functioning together will all abiotic factors of environment. Many species interdependent on each other. Involves energy flow + nutrient + gas exchanges.
Succession
Directional non-seasonal cumulative change in types of species that occupy given area through time. Involves changes to community, abiotic environment + interaction between these. Involves colonisation, establishment + extinction which act on participating plant species.
Seres
Stages in a succession which can be recognised by collection of species that dominate at that point in the succession.
Primary Succession
In previously uncolonised, newly formed barren land areas. Newly exposed land/rock provides harsh + hostile environment for life + no soil present to support plants. e.g sand dunes
Secondary Succession
Happens following destruction of existing ecosystem.
Pioneer Species
Usually R-Selected species with high levels of dispersal. e.g. lichens
Climax Community
Stable end of succession which is in equilibrium with environment. e.g. Broadleaf deciduous forests or moorland
Biotic Climax
Community where stable end stage of succession is maintained by biotic factors e.g. shading trees, heavy animal tramping. Differs from any other climax community.
Climatic Climax
Culminating stage of plant succession for given environment, vegetation has reached stable condition so long as environment stays same or changes only in response to climate/soil substrate changes which are slow relative to rate of plant succession. Dictated by climate.
Haemocytometer
An instrument for visual counting of the number of cells in a blood sample or other fluid under a microscope.
Lincoln Index
Statistical measure to estimate num of cases that haven’t yet been observed, based on 2 independent sets of observed cases.
R
Intrinsic rate of natural increase (biotic potential)
K
Carrying capacity.
Parasite
An organism that lives in or on another organism (host) benefiting from it and causing it harm over an extended period of time.
Resource
Supply of materials + other assets that can be drawn on by someone to function.
Competition
Striving to gain something by defeating others.
