Chapter 14

14-1

•A habitat differs from a niche.

A habitat is all aspects of the area in which an organism lives.

•Biotic factors – all living organisms within an ecosystem (ex. Birds, trees, bacteria)

•Abiotic factors – physical or non-living factors (ex. Climate, temperature, precipitation, wind sunlight, soil)

•Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.

•What biotic factor affects the size of a population? Number and kinds of predators in the ecosystem.

•Example of a change in an abiotic factor: No rain – mountain lion leaves his area to find water somewhere else.

•Resource availability gives structure to a community.

Species can share habitats and resources.

A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. For example, food, physical conditions, reproduction (when and how)….

•Can also be known as the role and position that a certain species of animal occupies.

•A fundamental rule in ecology, the competitive exclusion principle, states that no 2 species can occupy the same niche in the same habitat at the same time.Competitive exclusion keeps two species from occupying the same niche.

•The area where an organism lives that includes biotic and abiotic factors is called its habitat. Two species can share the same habitat, but not the same niche.

•Ecological equivalents are species that occupy similar niches but live in different geographical regions.

14-2

•Competition and predation are two important ways in which organisms interact.Community interactions, such as competition, predation, and various forms of symbiosis, can powerfully affect an ecosystem.

•Resource refers to any necessity of life, such as water, food, etc…

•Competition occurs when two organisms fight for thesame limited resource.

–Intraspecific competition

–Interspecific competition

–Predation occurs when one organism captures and eats another.(predator –

kills and eats; prey – food source)

Any relationship in which 2 species live closely together is called symbiosis.

•There are three major types of symbiotic relationships.

Parasitism: one organism benefits, the other is harmed. Parasites meet their needs as ectoparasites (such as leeches) and endoparasites (such as hookworms)

Mutualism - both species benefit from the relationship (flower and insects)

Commensalism - one benefits and the other is neither helped, nor harmed.

(barnacles onwhales)

14-3

•Population density is the number of individuals that live in a defined area.

Scientists can calculate population density.Population density is the number of individuals per unit area ex. 100/km2

Geographic dispersion of a population shows how individuals in a population are spaced.

•Population dispersion refers to how a population is spread in an area.

•There are three types of dispersion: clumped, uniform, random.

•Survivorship curves help to describe the reproductive strategy of a species.

•A survivorship curve is a diagram showing the number of surviving members over time from a measured set of births.

•Survivorship curves can be type I, II or III.

14-4

•Changes in a population’s size are determined by immigration, births, emigration, and deaths.

•The size of a population is always changing.

** A population will increase or decrease in size depending on how many individuals are added to or removed from the population.** ex. Many births increase population; a natural disaster such as a hurricane will decrease it.

A population can grow when its birthrate is greater than its death rate. Birthrate equals death rate, population stays the same. Death rate greater than birthrate, population decreases.

Immigration – movement of individuals into an area (population increase).

Emigration – movement of individuals out of a population (population decrease).

•Population growth is based on available resources.

Exponential growth is a rapid population increase due to an abundance of resources. Under ideal conditions, with unlimited resources, a population will grow exponentially

Logistic growth is due to a population facing limited resources. As resources become less available, the growth of a population slows or stops.

Carrying capacity is the maximum number of individuals in a population that the environment can support.

•Ecological factors limit population growth.

•A limiting factor is something that keeps the size of a population down.

Density-dependent limiting factors are affected by the number of individuals in a given area. Density dependent factors become limiting only when the population density reaches a certain level. Density dependent limiting factors include:

•Competition – when populations become crowded, organisms compete or struggle for food, water, space, and other essentials for life.

*the more organisms in an area, the sooner the resources will be used up

•Predation – the populations of predator and prey go up and down

*prey population increases, predator population increases; prey population decreases, predator population decreases; cycle starts again

•Parasitism- parasites take nourishment from host causing weakness or death, affecting population numbers.

•Disease

Density-independent limiting factors limit a population’s growth regardless of the density. Density-independent factors affect all populations in similar ways

Examples: 1) unusual weather

population2) natural disasters

crashes3) seasonal changes

then4) damming rivers

rebuilds5) cutting timber

14-5

Ecological Successionoccurs following a disturbance in an ecosystem

  • This series of predictable changes that occur in a community over time is called ecological succession.
  • 3 ways that ecological succession can happen (physical changes)
  1. slow physical changes over time (ex. Trees growing large)
  2. sudden natural or human disturbance (ex. Clearing a forest for land development)
  3. natural disaster (ex. Hurricane, tornado, eruption)
  • Primary Succession is when succession occurs on land surfaces where no soil exists, for example, rock, volcanoes….
  • The 1st species to populate the area are called pioneer species. Lichens are a pioneer species. They are made up of a fungus and an alga and can grow on bare rocks. As they grow, they break up rocks. When they die, they add organic material to help form soil in which other plants can grow.
  • Secondary Successionoccurs when a disturbance of some kind changes an existing community without removing the soil. (land cleared and plowed for farming and abandoned, wildfires) *Final stage of succession for a pond would be to fill with soil.
  • Factors that influence continual change: long-term climate changes, further disturbances, introduction of non-native species.
  • Natural disturbances interrupt succession.