VCE Biology Population Dynamics
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Transcript of VCE Biology Population Dynamics
VCE BIOLOGY
www.drlakshmisharma.comDr Lakshmi Sharma
NO LIMITS TO LEARNING! BELIEVE & YOU CAN ACHIEVE!
POPULATION DYNAMICS
Managing Populations
Abiotic & biotic factors
affect the abundance & distribution of organisms
Population explosion
a rapid increase in population size
Population decline
a decrease in population size
Sustainable use – to exist in the future
Harvesting of resources - drive species to extinction Some whale species have almost become extinct Sustainable use important - resources used in the future
Definitions - Distribution & Abundance
Population – no. organisms of the same species
that live in a defined geographic area
Distribution – Geographic range and preferred habitat
Abundance – Size of a population
Knowing the distribution & abundance of species is important for sustainability & existence - Wombat
Factors affecting distribution & abundance
Characteristics of the environment
light availability, temperature, tide
Characteristics of the organism
methods of eating, reproducing etc.
Interactions between organisms
distribution is limited by availability of prey/abundance of predators & competition for food and shelter.
Reasons for Abundance
Nomadic – flies from pond to pond in search of places to feed and breed.
Lives in temporary, shallow waters which are often rich in food
They breed when flood waters rise and food/nest holes are abundant. (Courting and mating occurs quickly)
Reasons for Abundance cont’d
They eat a wide range of food (insects, molluscs, crustaceans, seeds, fruits)
Have no important predators
Is not in direct competition with other duck species
What determines size of population?
BirthDeath Immigration arriving from outside of a
populationEmigration out of a population
Populations
A rapid increase in population size –
EXPONENTIAL GROWTH
Population density limits pop growth - Intra
specific competition
The carrying capacity of an ecosystem death
= birth – constant
Population Explosions
Aquatic weeds – Salvina Fern – native to Brazil-2-5 days doubles pop.
Crown of thorns sea star – infestations damage coral reef – 14% of GBR infested
Population Explosions
Why?
Reproduction-ability to reproduce at greater rate
Favourable abiotic environment Lack of predators Dispersal factors carry to new area
Introduction of New Species
Boneseed from South Africa invaded coastal sand dunes in E. Australia
English broom weed threatens survival of native plants Camel survived in Australia now extinct in its native north
Africa & Arabia. Abundant pests include European Carp, mosquito fish,
water buffalo, the cane toad, the European rabbit, mice & red fox.
Introduction of New Species
Control of Pests
Prickly pear cactus -24m hectares- biological agent -moth ate plant
Rabbit-myxomatosis – resistance-rabbit calicivirus disease (1996)
Cane toads-control pest for cane beetles-did not control beetles and became pest