Population dynamics

Population dynamics

1. POPULATION DYNAMICS Population dynamics  refers to how populations of a species change over time.  A  population   is a group of individuals of the same species that occupy a specific area over a certain period of time. The different studies about population of organisms is known as population ecology. An   ecologist  is a scientist who studies how animals and plants interact with their environment.

2. Population density Spatial distribution patterns Population range Reproduction patterns Population characteristics

3. Population Density Population density =    A  population density   - the number of individuals occupying a certain area.

4. Population density =   Computing for the population densities of organisms in previous slide. Population B Population density = 10 ducks (4m) (2m) = 10 ducks   = 1.25 ducks   Population A Population density = 2 0 ducks (4m) (2m) = 2.5 ducks   = low density = high density

5. Spatial Distribution Pattern Scientists classify dispersion patterns into 3 types: Uniform dispersion Clumped dispersion Random dispersion   Dispersion – is the pattern of spacing among members of population with in a specified area.

6. Types of dispersion patterns 1. Uniform Distribution It maintain defined territories .

7. Types of dispersion patterns 2. Clumped Distribution - is when individuals in a population are clustered together, creating some patches with many individuals and some patches with no individuals. 

8. Types of dispersion patterns 3. Random Distribution   - individuals are distributed randomly, without a predictable pattern.

9. Other conditions can limit population range such as: Amount of rainfall Sudden changes in temperature Biotic factors like the presence of predators and competitors Population Range - the occupancy of some species in a certain area.

10. Reproduction Patterns Some organisms produce many, small-sized offspring all at once, with little or no parental care or protection. This kind of reproductive strategy found among: Bacteria Algae insects Other organisms tend to produce a small number of offspring with fairly long life spans. Example – mammals produce their young inside their womb to give their optimum protection. After birth, the offspring will be nourished and protected until they can live on their own.

11. LIMITING POPULATION GROWTH Two categories or limiting factors Density – independent factor affect the population regardless of its density. Usually abiotic factor. 2. Density – dependent factor - depend on the number of members in a population. These factors include exposure to infectious diseases, predation and competiton for food. Limiting factors – any biotic and abiotic factor that restricts the number of reproduction of organisms in an ecosystem.

12. All factors that limit population size are called environmental resistance. The number of organisms that can be supported by a given environment refers to its carrying capacity .

13. Population variable s Birth rate Death rate Emigration immigration Birth rate – refers to the number of individual births in a population in a certain period of time. Death rate – indicates the number or deaths in a certain population in a given time. If death rate is higher than birth rate, population size decreases. If birth rate is higher than death rate, population size increases.

14. Immigration – refers to the movement of individual member of a population into another group of population. Emigration – happens when some members leave the group. For animals a search for new food will cause them to migrate into a new home.

15. To compute the population change in an environment Population change = (births + immigration ) – (deaths + emigration)

16. ECOSYSTEM STABILITY An ecosystem is stable when it has the ability to maintain its structure and function over long periods of time despite disturbances. To achieve stability, an ecosystem must fulfill two components: 1. Resistance – an ecosystem shows resistance when its structure and functions stay normal despite changes in the environment. 2 . Resilience – when it regain its normal structure and function after a disturbance.

17. Species richness – the number of different species that thrive in an area, is a measurable quantity used by scientist to predict the stability of ecosystems. Keystone species – certain types of organisms which perform unique functions in the ecosystem. Examples: Sharks Alligators cats

18. Thank you Reference: Phoenix Publishing House Exploring Life Through Science – The New Grade 10