introduction to ecologyagho.weebly.com/uploads/2/2/9/4/22942978/ecology_v2__1_.pdf · evolution...
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ECOLOGY
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ECOLOGY
• Study of interactions between organisms and the environment
• Abiotic- nonliving components
• Biotic- living components
• Environmental components
• Affect the distribution and abundance of organisms
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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
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BIOGEOGRAPHY
• Provides a good starting point for understanding what limits the geographic distribution of species
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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
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DISTRIBUTION
• Biotic factors- Interactions with other species
• Predation
• Competition
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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
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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
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CLIMATE FACTORS • Sunlight intensity
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• Air circulation and wind patterns
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BODIES OF WATER
• Oceans and their currents, and large lakes
• Moderate the climate of nearby terrestrial environments
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• Lakes
• Are sensitive to seasonal temperature change
• Experience seasonal turnover
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MOUNTAINS
• Mountains have a significant effect on
• The amount of sunlight reaching an area
• Local temperature
• Rainfall
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ANIMAL BEHAVIOR
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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?
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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
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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
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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
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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
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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
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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
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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
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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
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MIGRATION • Many features of migratory behavior in birds
• Have been found to be genetically programmed
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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
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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
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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
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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
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• 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
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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
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• Example: Operant conditioning • In which an animal learns
to associate one of its behaviors with a reward or punishment
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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
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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
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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
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VARIATION IN AGGRESSION
• Funnel spiders living in different habitats
• Exhibit differing degrees of aggressiveness in defense and foraging behavior
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FORAGING BEHAVIOR
• Studies of Drosophila populations raised in high- and low-density conditions • Show a clear divergence in
behavior linked to specific genes
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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
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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
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• In species that produce large numbers of offspring
• Parental care is at least as likely to be carried out by males as females
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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
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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
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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
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• The size of eyestalks in stalk-eyed flies
• Affects which males the females choose to mate with
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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
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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
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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
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INCLUSIVE FITNESS AND ALTRUISM
• In naked mole rat populations
• Non-reproductive individuals may sacrifice their lives protecting the reproductive individuals from predators
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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
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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
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