Aquatic ecology and Biodiversity

Unit 3- Population ecology

3.16.Regulation of population density
The total number of individuals of a species living in an area is called population density. Population grows by reproduction of individuals.
Eg: An oyster lays about 50 million eggs. If all egg hatches,they will form a volume about eight time the size of the earth Though the reproductive rate is high, the population does not increase as expected. This is because the density is regulated.
• Density dependent factors
• Density independent factors

Density independent factors
They are connected with population density – Extrinsic factors.
Eg: Food, space, shelter and weather
When 100 ornamental fishes are introduced into a small aquarium tank most of them die because of starvation and shortage of space.
Density dependent factors
They are intrinsic factors arise within the population during their growth.
• Competition – Competition for common resource – space food, mate etc..
• Predation – Killing (predator) other animal (prey) for food.
• Emigration - Displacement of organisms
• Reproductive – Decreases the reproductively by increasing the density
• Diseases – Kills the individuals and reduces the population