Population Flashcards
(23 cards)
What is a population
A group of organisms of the same species living in a particular area
What is population growth
The change in the number of organisms
-increase occurs when a bacterium divides to produce 2 daughter cells
Describe the LAG phase
-Slow growth
-nutrient assimilation occurs- bacteria activating genes to produce the appropriate enzymes to metabolise a particular food substrate
Describe the EXPONENTIAL phase
-Bacteria divides exponentially
-no growth restrictions- abundant resources and no toxic waste accumulation
-bacteria divide to produce new bacteria
Describe the STATIONARY phase
-food supplies are limiting
-no. of new individuals fall
-waste products/ toxics accumulate to a level that restricts growth
-birth and death rates accumulate
Describe the DECLINE phase
-Death rates exceed birth rates
-population declines- population ‘crash’
-due to waste accumulation and nutrient supply running out
What is biotic potential
The reproductive rate of a population under optimum conditions with unlimited resources
What is environmental resistance
The restriction by the environment on the population reaching its maximum growth rate and biotic potential
What is the carrying capacity
The maximum number of organisms an ecosystem can support- determined by resources
What is competition between organisms
When different species are competing for the same resource
-Important for providing environmental resistance and carrying capacity
What is intraspecific competition
Competition between same species
What is interspecific competition
Competition between different organisms
What are r-selected species
-opportunistic
-grow quickly
-inhabit unstable and short lived habitats
-poor parental care
-small body size
-low competitive ability- unlikely to become dominant
What are k-selected species
-large body size
-long life cycle
-large parental care- high investment in young- few young produced so important they have a high chance of survival
-more constant size
-high competitive ability- likely to be come dominant
-inhabit stable habitats
What is a parasite
Can be defined as an organism that lives in or on the host, benefitting from it and causing it harm over an extended period of time
Why do parasites differ from predators
-parasite lives in or on the host
-parasite causes harm to the host over an extended period of time
-parasite is usually smaller than the host
-parasite seldom kills the host
What is a pest species
A species that damages a valuable/ commercial crop species, causing economic damagae
What is biological control
Deliberately introducing an organism that will target and harm the pest. Can be a predator, competitor, parasite or pathogenic organism
Why does biological control work
-will benefit the environment by reducing the need for chemical pesticides and harm
-broad spectrum pesticides may not work well- broad spectrum pesticides may kill beneficial organisms, inc many natural enemies of the pest
What is pest resurgence
When the numbers increase rapidly due to the elimination of a natural predator
-in pest resurgence after the use of insecticide, the no rise to well above what it was before it was added
What is effective biological control
The introduced predator integrates naturally into the ecosystem, building a sustainable population and therefore does not need to be continually intorduced
What are the advantages of effective biological control
-no chemical damage to the environment with the risk of significant ecological harm and bioaccumulation in food chains
-biological control targets only the pest species- reduced collateral damage affecting other organisms
-the development of resistance to pests is unlikely
-pest resurgence is unlikely
-if successful, biological control needs little additional action so saves money on continued use of pesticides.
What are the disadvantages of effective biological control
-pest is unlikely to be totally eliminated
-will only work well if the biological control species can adapt well and thrive in the ecosystem introduced
-important that the introduced species does not outcompete native species (cause harm to non-target species)
