LO’s

- the meaning of ecology, population symbiotic relationships- can explain population demographics and ways in which population sizes are regulated.- can explain various types of symbiotic relationships.

Ecology Population

Ecology• Study of the interactions between organisms and the

environment• Study of the physical and biological variables

governing the distribution & growth of living things

Population • Individuals of a given species occurring at one

place at one time• Population ecology– Study of population growth & interactions

Population

Is a groups of individual of the same species that live in the same area

1. Population Density:

2. Spatial Distribution:• Dispersion: The pattern of spacing a population within

an area (Way that individuals are arranged• 3 main types of dispersion• Clumped• Uniform• Random

Population Characteristics

• Number of organisms per unit area• Density influences survival

• Individuals evenly spaced• Often results from territoriality• Also plants with allelopathy

• Lacking definite order• Individuals do not influence

others growth

• Individuals form clusters• Clumping due to interaction of

individuals

Population Limiting Factors

3. Population growth rate– How fast a given population

grows– Factors that influence this

are:• Natality • Mortality• Emigration - movement

out of a population• Immigration - movement

into a population

Population Size

• (births + immigrants) – (deaths + emmigrants) = Population change

• Immigration – movement into a population

• Emigration – movement out of a population

Carrying Capacity• Indefinite exponential growth is limited• Shortages of growth factors will limit population

growth• Carrying capacity = maximum number that can be

supported in a particular environment

Population size

(births + immigrants) – (deaths + emigrants) = Population change

Boom & Bust Cycle

• Sometimes populations do not level off• Exponential growth with a sudden die-off

Interactions Within Communities

Community• Grouping of populations living together in a

particular area at a particular time

Abiotic Factors• Nonliving factors

within the environment– Air– Water– Rocks

• Abiotic factors affect living (biotic) factors

Biotic components are the living things that shape an ecosystem.

Biotic factor - any living component that affects another organism - needs energy to do work and food for proper growth - Plants, animals, fungi, protiste and bacteria

Ecosystem• Biotic & abiotic factors in a certain area• Biotic and abiotic factors combine to create a system

(ecosystem)

Habitat

• Space within an area where an organism lives

• Each organism plays a certain role

Niche• Two ways of defining– An organism’s role in the environment– Organism’s use of biotic & abiotic resources

Density Dependent Factors

• Factors that affect a population only if its density changes• Types of density dependent factors– Competition – Predation – Parasitism

Competition

• Interaction among organisms for the same resources– Food– Living space

• Regulates population size & is a driving force of evolutionary change

Competition Types• Intraspecific – among the same species• Interspecific – between species

Predation

• One species will kill & eat another

• Interactions maintain natural populations

• More prey results in more predators

• Less prey reduces predator numbers

Parasitism• One species living at the expense of another• Regulates populations by weakening or killing

Symbiosis is a close relationship between two or more different species.

There are 3 types of symbiosis we will discover:

Commensalism—A relationship where one species obtains food or shelter from the other species. Does not harm or help the other species.

Mutualism—A relationship where both species benefit from the relationship

Parasitism-- A relationship between two species in which one species (the parasite) nourishes itself to the disadvantage of the other species (the host).

Demography• Statistical study of human population • Human population is in exponential growth

Human Population Growth has Different Patterns

• Stable population– Remains the same– Same number entering reproductive age as at

end of reproductive age

• Population pyramid– Graphic representation of population age– Shows patterns in population change

Biotic and abiotic factors are interrelated. If one factor is changed or removed, it impacts the availability of other resources within the system