Biology Unit 8

Ecology

Ecology

The scientific study of the interactions between organisms and the environment. The interactions determine both the distribution of organisms and their abundance.

Events that occur in ecological time…

Affect life on the scale of evolutionary time

Abiotic

Non living components

Biotic

Living components

Biota

All the organisms living in the environment

Environmental components…

Affect the distribution and abundance of organisms

Organismal ecology

Studies how an organism’s structure, physiology, and behavior (for animals) meet the challenges posed by the environment

Population ecology

Concentrates mainly on factors that affect how many individuals of a particular species live in an area

Community ecology

Deals with the whole array of interacting species in a community

Ecosystem ecology

Emphasizes energy flow and chemical cycling among the various biotic and abiotic components

Landscape ecology

Deals with arrays of ecosystems and how they are arranged in a geographic region

Biosphere

The global ecosystem, or sum of all the planet’s ecosystems

The precautionary principle

States that humans need to be concerned with how their actions affect the environment

Interactions between organisms and the environment…

Limit the distribution of species

Biogeography

Provides a good starting point for understanding what limits the geographic distribution of species

Dispersal

The movement of individuals away from centers of high population density or from the area of origin and contributes to the global distribution of organisms

Species transplants

Include organisms that are intentionally or accidentally relocated from their original distribution and can often disrupt the communities or ecosystem to which they have been introduced

Habitat Selection

Some organisms do not occupy all of their potential range and may be limited by habitat selection behavior

Biotic factors that affect the distribution of organisms

Interactions with other species, predation, competition

Abiotic factors that affect the distribution of organisms

Temperature, water, sunlight, wind, rocks and soil

Environmental temperature…

Is an important factor in the distribution of organisms because of its effects on biological processes

Water availability among habitats

Another important factor in species distribution

Sunlight affects distribution

Light intensity and quality can affect photosynthesis in ecosystems, and is also important to the development and behavior of organisms sensitive to the photoperiod

Wind affects distribution

Amplifies the effects of temperature on organisms by increasing heat loss due to evaporation and convection, and can also change the morphology of plants

Characteristic of soil that limit distribution of plants and thus animals

Physical structure, pH, mineral composition

Four major abiotic components make up climate

Temperature, water, sunlight, wind

Climate

The prevailing weather conditions in a particular area

Microclimate

Patterns on the global, regional, and local levels

Microclimate

Very fine patterns, such as those encountered by the community of organisms underneath a fallen log

Earth’s global climate patterns…

Are determined largely by the input of solar energy and the planet’s movement in space

Sunlight intensity…

Plays a major part in determining the Earth’s climate patterns (sunlight hitting earth directly overhead makes the Equator warmer, whereas sunlight coming at a low angle make it colder)

Air circulation and wind patterns…

Play major parts in determining the Earth’s climate patterns. Ascending moist air releases moisture, and descending dry air absorbs moisture.

Various features of the landscape…

Contribute to local variations in climate

Oceans and currents, and large lakes…

Moderate the climate of nearby terrestrial environments. Warm air over land rises, air cools at high elevation over the ocean, cooler air sinks over water, and cool air over water moves inland, replacing the rising warm air over land.

Mountains have a significant effect on…

The amount of sunlight reaching an area

Local temperature

Rainfall: as moist air comes from the ocean and moves into mountains, it flows upward, cools at higher altitudes, and drops large amounts on water. Farther inland, precipitation increases again as the air moves up over the mountains and once it passes the mountain, there is little precipitation as it all dropped on one side of the mountain.

The angle of the sun…

Leads to many seasonal changes in local environments

Lakes…

Are sensitive to seasonal temperature change and experience seasonal turnover. In winter, the water at the surface (ice) is the coldest, then in spring, the sun melts the ice and the surface water warms and sinks below the cooler layers. In summer, the water returns to thermal stratification (layers). Then the surface cools in fall and remixes the water.

Microclimate…

Is determined by fine-scale differences in abiotic factors

One way to predict future global climate change…

Is to look back at the changes that occurred previously

Biomes

The major types of ecological associations that occupy broad geographic regions of land or water.

Aquatic biomes…

Account for the largest part of the biosphere in terms of area and contain fresh or salt water

Oceans…

Cover about 75% of Earth’s surface and have an enormous impact on the biosphere

Many aquatic biomes…

are stratified into zones or layers defined by light penetration, temperature, and depth

Climate…

Largely determines the distribution and structure of terrestrial biomes and is particularly important in determining why particular terrestrial biomes are found in certain areas

Terrestrial biomes

Names for major physical or climatic factors and for their predominant vegetation

Behavioral ecology

Extends observations of animal behavior by studying how such behavior is controlled and how it develops, evolves, and contributes to survival and reproductive success

Proximate cause of behavior (how)

Those that focus on the immediate stimulus and mechanism for the behavior (environmental stimuli).

Ultimate cause (why)

Those that explore how the behavior contributes to survival and reproduciton

Behavior

Is what an animal does and how it does it (includes muscular and nonmuscular activity)

Learning

Also considered a behavioral process

Ethology

The scientific study of animal behavior, particularly in natural environments.

Fixed action pattern (FAP)

In a sequence of unlearned, innate behaviors that is unchangeable. Once initiated, is usually carried to completion.

Sign stimulus

What triggers the fixed action pattern

Imprinting

A type of behavior that includes both learning and innate components and is generally irreversible.

It is distinguished from other types of learning by a sensitive period which is a limited phase in an animal’s development that is the only time when certain behaviors can be learned.

Ex: young geese following their mother. Proximate cause is young geese observing mother moving away from them and calling. Ultimate cause is the geese that imprint on mother receive more care and learn necessary skills for survival.

Many behaviors…

Have a strong genetic component

Directed movements

Animal movements that are under substantial genetic influence

Kinesis

A simple change in activity or turning rate in response to a stimulus. (Ex: sow bugs that increase activity in dry areas and less in humid areas)

Taxis

Is a more or less automatic, oriented movement toward or away from a stimulus. (Ex: fish automatically swim in an upstream direction)

Migration…

Many features of migratory behavior in birds have been found to be genetically programmed

Signal (behavioral ecology)

A behavior that causes a change in another animal’s behavior.

Communication

The reception of and response to signals

Animals communicate using…

Visual, auditory, chemical, tactile, and electrical signals. The type of signal used to transmit information is closely related to an animal’s lifestyle and environment.

Chemical communication

Many animals that communicate through odors emit chemical substances called pheromones

Auditory communication

Have shown that courtship songs are under genetic control.

Learning

The modification of behavior based on specific experiences. They range from very simple to very complex.

Habituation

The loss of responsiveness to stimuli that convey little or no information.

Spatial learning

The modification of behavior based on experience with the spatial structure of the environment

Cognitive map

An internal representation of the spatial relationships between objects in an animal’s surroundings

Associate learning

Animals associate one feature of their environment with another

Classical conditioning

A type of associative learning in which arbitrary stimulus is associated with a reward or punishment

Operant conditioning

A type of associative learning in which an animal’s lifestyle learns to associate one of its behaviors with a reward or punishment

Cognition

The ability of an animal’s nervous system to perceive, store, process, and use information gathered by sensory receptors.

Problem solving…

Can be learning by observing the behavior of other animals, but genetics and environment can interact to influence the learning process.

Behavioral traits…

Can evolve by natural selection (and environment)

Natural selection can result in the evolution of behavioral traits in populations

Natural selection

Natural selection favors behaviors that increase survival and reproductive success and the genetic components of behavior evolve through natural selection

Behavior can also affect fitness through its influence on foraging and mate choice

Optimal foraging theory

Views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food

Mating behavior

The product of a form of natural selection called sexual selection and the relationship between males and females varies a great deal from species to species.

Promiscuous mating

Occurs in many species with no strong pair-bonds or lasting relationships

Monogamous relationships

When one male mates with one female

Polygyny

One male mates with many females and the males are often more showy and larger than the females.

Polyandrous systems

One female mates with many males and the females are often more showy than the males.

Certainty of paternity

Influences parental care and mating behavior

Parental care in large offspring

Parental care is limited in species that produce large numbers of offspring

Intersexual selection

Members of one sex choose mates on the basis of particular characteristics and involves competition among members of one sex for mates

Agonistic behavior

An often ritualized contest that determines which competitor gains access to a resource

Game theory

Where the mating outcome depends on each individual’s strategy and the strategy of other individuals

Inclusive fitness…

can account for most altruistic social behavior, though many social behaviors are selfish

Altruism

When some animals behave in ways that reduce their individual fitness but increase the fitness of others

Inclusive fitness

The total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables close relatives to produce offspring

Hamilton’s rule

A quantitative measure for predicting when natural selection would favor altruistic acts among related individuals. The key variables include the benefit to the recipient, the cost to the altruist, and the coefficient of relatedness.

Natural selection favors altruism when the benefit to the recipient multiplied by the coefficient of relatedness exceeds the cost to the altruist.

Coefficient of relatedness

The probability that two relatives may share the same genes

Kin selection

The natural selection that favors altruistic behavior by enhancing reproductive success of relatives.

Reciprocal altruism

When altruistic behavior toward unrelated individuals is adaptive and the aided individual returns the favor in the future.

Culture

A system of information transfer through observation or teaching that influences the behavior of individuals in a population

Mate choice copying

A behavior in which individuals in a population copy the mate choice of others

Density

The number of individuals per unit area or volume. It is very difficult to determine the density of natural populations. It is the result of dynamic interplay between processes that add individuals to a population and those that remove individuals from it.

Dispersion

The pattern of spacing among individuals within the boundaries of the population

Clumped dispersion

One in which individuals aggregate in patches and may be influence by resource availability and behavior.

Uniform dispersion

One in which individuals are evenly distributed and may be influenced by social interactions such as territoriality.

Random dispersion

One in which the position of each individual is independent of other individuals.