Ecology Population

CONCEPT OF BIOLOGY; BGY 2001

Dr Mashitah Shikh Maidin

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).

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