ECOLOGY

ECOLOGY

• Study of interactions between organisms and the environment

• Abiotic- nonliving components

• Biotic- living components

• Environmental components

• Affect the distribution and abundance of organisms

LEVELS OF ECOLOGICAL STUDY • Organismal

• Structure, physiology, and (for animals) behavior meet the challenges posed by the environment

• Population • Factors that affect how many individuals of a

particular species live in an area

• Community • Interactions between members of different

species

• Ecosystem • Energy flow and chemical cycling among biotic

and abiotic components

• Biome/Biosphere • Deals with arrays of ecosystems and how they are

arranged in a geographic region

BIOGEOGRAPHY

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

DISPERSAL AND DISTRIBUTION

• Dispersal

• Movement of individuals away from centers of high population density or from their area of origin

• Contributes to the global distribution of organisms

• Natural range expansions- show influence of dispersal on distribution

DISTRIBUTION

• Biotic factors- Interactions with other species

• Predation

• Competition

DISTRIBUTION: ABIOTIC FACTORS

• Temperature- rate of biological reactions

• Water

• Sunlight- photosynthesis and photoperiods

• Wind- Amplifies effects of temperature

• Rocks and soil- limit the distribution of plants and thus the animals that feed upon them

• Physical structure

• pH

• Mineral composition

CLIMATE

•Prevailing weather conditions in a particular area

• Four abiotic components

• Temperature, water, sunlight, and wind

•Global climate patterns- determined largely by the input of solar energy and the planet’s movement in space

CLIMATE FACTORS • Sunlight intensity

• Air circulation and wind patterns

BODIES OF WATER

• Oceans and their currents, and large lakes

• Moderate the climate of nearby terrestrial environments

• Lakes

• Are sensitive to seasonal temperature change

• Experience seasonal turnover

MOUNTAINS

• Mountains have a significant effect on

• The amount of sunlight reaching an area

• Local temperature

• Rainfall

ANIMAL BEHAVIOR

ETHOLOGY

• Ethology is the scientific study of animal behavior

• Particularly in natural environments

• Set of questions • What is it for?

• How did it develop during the lifetime of the organism?

• How did it develop during the history of the species?

• How does it work?

CAUSES OF BEHAVIOR

• Behavioral ecologists distinguish between proximate and ultimate causes of behavior

• The scientific questions that can be asked about behavior can be divided into two classes

• Those that focus on the immediate stimulus and mechanism for the behavior

• Those that explore how the behavior contributes to survival and reproduction

PROXIMATE AND ULTIMATE QUESTIONS

• Proximate, or “how,” questions about behavior

• Environmental stimuli that trigger a behavior

• Genetic, physiological, and anatomical mechanisms underlying a behavioral act

• Ultimate, or “why,” questions about behavior

• Address the evolutionary significance of a behavior

BEHAVIOR

• Biologists study the ways both genes and the environment

• Influence the development of behavioral phenotypes

• Innate- Behavior that is developmentally fixed

• under strong genetic influence

• Learned- behavior that is modified by experience

KINESIS • A kinesis

• Is a simple change in activity or turning rate in response to a stimulus

• Sow bugs

• Become more active in dry areas and less active in humid areas

TAXIS • A taxis

• Is a more or less automatic, oriented movement toward or away from a stimulus

• Many stream fish exhibit positive rheotaxis

• Where they automatically swim in an upstream direction

FIXED ACTION PATTERNS

• A fixed action pattern (FAP)

• Is a sequence of unlearned, innate behaviors that is unchangeable

• Once initiated, is usually carried to completion

• A FAP is triggered by an external sensory stimulus

• Known as a sign stimulus

FAP EXAMPLE

• In male stickleback fish, the stimulus for attack behavior • Is the red underside of an

intruder

• When presented with unrealistic models • As long as some red is present,

the attack behavior occurs

• Proximate and ultimate causes for the FAP attack behavior in male stickleback fish

IMPRINTING • Imprinting is a type of behavior

• That includes both learning and innate components and is generally irreversible

• Imprinting is distinguished from other types of learning by a sensitive period • A limited phase in an animal’s development that is the only time

when certain behaviors can be learned

• An example of imprinting is young geese • Following their mother

• Konrad Lorenz showed that • When baby geese spent the first few hours of their life with him, they

imprinted on him as their parent

MIGRATION • Many features of migratory behavior in birds

• Have been found to be genetically programmed

ANIMAL SIGNALS AND COMMUNICATION

• Signal - a behavior that causes a change in another animal’s behavior

• Communication- 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 COMMUNICATIONS • Animals communicate through odors

• Pheromones

• When a minnow or catfish is injured

• An alarm substance in the fish’s skin disperses in the water, inducing a fright response among fish in the area

ENVIRONMENT AND BEHAVIOR • Example:

• Diet and mate selection by Drosophila mojavensis

• That the type of food eaten during larval development influences later mate choice in females

LEARNING

• Learning is the modification of behavior

• Based on specific experiences

• Learned behaviors

• Range from very simple to very complex

• Habituation

• Is a loss of responsiveness to stimuli that convey little or no information

• Spatial learning • Based on experience with the

spatial structure of the environment

• Cognitive map • Internal representation of the

spatial relationships between objects in an animal’s surroundings

ASSOCIATIVE LEARNING • Animals associate one

feature of their environment with another

• For example: Classical conditioning • An arbitrary stimulus is

associated with a reward or punishment

• Example: Operant conditioning • In which an animal learns

to associate one of its behaviors with a reward or punishment

BEHAVIORAL VARIATION AND EVOLUTION

• When behavioral variation within a species • Corresponds to variation in the

environment, it may be evidence of past evolution

• Differences in prey selection in populations of garter snakes • Are due to prey availability and are

evidence of behavioral evolution • Coastal snakes eat banana slugs, inland

snakes do not • Even young snakes reared in captivity

exhibit this preference

COGNITION AND PROBLEM SOLVING

• Cognition is the ability of an animal’s nervous system

• To perceive, store, process, and use information gathered by sensory receptors

• Problem solving can be learned

• By observing the behavior of other animals

BEHAVIOR AND EVOLUTION

• Natural selection favors behaviors that increase survival and reproductive success

• Behavior can affect fitness

• Through its influence on foraging and mate choice

VARIATION IN AGGRESSION

• Funnel spiders living in different habitats

• Exhibit differing degrees of aggressiveness in defense and foraging behavior

FORAGING BEHAVIOR

• Studies of Drosophila populations raised in high- and low-density conditions • Show a clear divergence in

behavior linked to specific genes

FORAGING • Optimal foraging theory

• Compromise between the benefits of nutrition and the costs of obtaining food

• Example: crows eat molluscs called whelks • But must drop them from the air to crack

the shells

• Optimal flight height- Correlated with a fewer number of drops, indicating a trade-off between energy gained (food) and energy expended

MATING BEHAVIOR

• Varies a great deal from species to species

• In some species, mating is promiscuous

• With no strong pair-bonds or lasting relationships

• Influences on mating behavior: • The needs of the young

• The certainty of paternity

• In species that produce large numbers of offspring

• Parental care is at least as likely to be carried out by males as females

MATING SYSTEMS

• In monogamous relationships • One male mates with one female

• In a system called polygyny • One male mates with many

females • The males are often more showy

and larger than the females

• In polyandrous systems • One female mates with many

males • The females are often more showy

than the males

SEXUAL SELECTION

• In intersexual selection

• Members of one sex choose mates on the basis of particular characteristics

• Intrasexual selection

• Involves competition among members of one sex for mates

SEXUAL SELECTION

• Mate Choice by Females

• Male zebra finches • Are more ornate than

females, a trait that may affect mate choice by the females

• Imprinting of female chicks on males with more ornamentation • Affects mate selection

as adults

• The size of eyestalks in stalk-eyed flies

• Affects which males the females choose to mate with

SEXUAL SELECTION • Male competition for mates

• intrasexual selection that can reduce variation among males

• Such competition may involve agonistic behavior

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

GAME THEORY • Game theory evaluates alternative

behavioral strategies in situations

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

• Mating success of male side-blotched lizards

• Was found to be influenced by male polymorphism and the abundance of different males in a given area

• Rock-Paper-Scissors

INCLUSIVE FITNESS AND ALTRUISM

• Many social behaviors are selfish

• Natural selection favors behavior

• That maximizes an individual’s survival and reproduction

• On occasion, some animals

• Behave in ways that reduce their individual fitness but increase the fitness of others

• This kind of behavior

• Is called altruism, or selflessness

INCLUSIVE FITNESS AND ALTRUISM

• In naked mole rat populations

• Non-reproductive individuals may sacrifice their lives protecting the reproductive individuals from predators

HAMILTON’S RULE AND KIN SELECTION

• Hamilton proposed a quantitative measure

• For predicting when natural selection would favor altruistic acts among related individuals

• The three key variables in an altruistic act are

• The benefit to the recipient

• The cost to the altruist

• The coefficient of relatedness

• The coefficient of relatedness

• Is the probability that two relatives may share the same genes

HAMILTON’S RULE AND KIN SELECTION • Natural selection favors altruism when

the benefit to the recipient exceeds the cost to the altruist

• Coefficient of relatedness

• Hamilton’s rule

• Kin selection

• Favors this kind of altruistic behavior by enhancing reproductive success of relatives