8.1 Responses to the Environment

Ethology

the study of how evolutionary processes shape inherited behaviors and the ways that animals response to specific stimuli

Behavior

an animal’s response to a stimulus (internal or external)

nature vs nurture (genetic and environmental factors)

allows for survival and reproduction (subject to natural selection)

Proximate Cause

how a behavior occurs or how it is modified

1. What was the stimulus to cause the behavior?

2. How does the nurture component affect behavior? (how do the experiences during growth and development influence the response)

Ultimate Cause

why a behavior occurs (in context of natural selection)

1. How does the behavior help the animal survive and reproduce?

2. How does the nurture component affect behavior? (what is the evolutionary basis of the behavior?)

Innate behaviors

developmentally fixed

born behaviors, do not need to learn them: instinctive

fixed action patterns

note: while behaviors may learn more one way than the other, all behavior has a genetic basis, and all behaviors can be shaped by the environment. Think of behavior like a spectrum (from strongly influenced by genetics to strongly influenced by experiences)

Fixed action patterns

a sequence of unlearned acts directly linked to a stimulus

-actions are unchangeable

-carried out to completion

-triggered by a sign stimulus (external cue)

Learned behaviors

behaviors shaped by experiences

imprinting, spatial learning, associate learning, social learning

Imprinting

a long-lasting behavioral response to an individual
occurs during a sensitive/critical period early in life

ex. ducklings following their mother

Spatial learning

establishing memories based upon the spatial structure of the animal’s surroundings

some animals form a cognitive map or use landmarks as environmental cues

Associative learning

the ability to associate one environmental feature with another

ex. associating monarch butterflies with a foul taste

Social learning

learning through observations and imitations of the observed behaviors

ex. chimps breaking open oil palm nuts

Biological clock

internal mechanisms that regulate the timing of physiological processes and behaviors in response to environmental cues: can sustain biological rhythms independently

circadian rhythm

Circadian Rhythm

internal rhythm that follows a roughly 24 hour clock cycle

regulates activities (ex. sleep, feeding, hormone release)

ex. diurnal: most active during the day

nocturnal: most active during the night

crepuscular: most active at dawn or dusk

Directed movements

movements towards or away from a stimulus

Kinesis

a change in the rate of movement or the frequency of turning movements in response to a stimulus

nondirectional

Taxis

directional movement towards (positive) or away from (negative) a stimulus

phototaxis

chemotaxis

geotaxis

Phototaxis

movement in response to light

Chemotaxis

movement in response to chemical signals

Geotaxis

movement in response to gravity

Migration

a regular, long distance change in location

triggered by:

sun’s position

Earth’s magnetic field

Celestial cues

Phototropism

a directional response that allows plants to grow towards (and in some cases away from) a source of light

Photoperiodism

allows plants to develop in response to day length

plants flower only at certain times of the year

Soil Composition

soil composition can affect plants

the pH of soil can affect flower coloring in some plants

nutrients are more accessible at certain pH

ex. hydrangea blooms turn different colors based upon soil pH, for blue pH is 5 and for pink the pH is 7

Plant Mechanisms

plants have mechanisms defending themselves against herbivory

physical defenses: thorns, trichomes

chemical defenses: production of toxic or distasteful compounds

ex. lima bean plants that are being damaged release volatile chemicals that surrounding lima bean plants can sense, causing them to release compounds making themselves less susceptible to herbivory (herbivores)

Communication in Organisms

organisms must be able to detect and respond to information in order to survive and reproduce

Communication Signals

a stimulus generated and transmitted from one animal to another, animal communication

subject to natural selection

ex. visual, auditory, tactile, electrical, chemical

organisms use a combination of communication techniques

Visual Signals

behaviors or physical traits that can be seen

coloration: male peacocks displaying feathers to attract a mate, brightly colored flowers to attract pollinators

Auditory Signals

sounds produced by organisms

mating: males may produce songs/sounds to attract a mate

warning: alarm calls in meerkats or prairie dogs to warn off predators

establish territory: male birds will sing songs to announce their territory

Tactile Signals

communication through touch/physical contact

grooming: primates groom each other to bond

dance: bees perform a waggle dance in their dark hive to communicate the distance and direction of a food source, bees in close proximity to the dancer feel direction, distance, and speed of the bee’s movement

Electrical Signals

hunting: sharks, rays, and other electric fish send electrical signals through the water to locate prey

Chemical Signals

pheromones enlisted by members of a species that can affect other members of the same species

foraging: ants following pheromone trail to food source

marking: animals may mark territory with scent

warnings: alarm pheromones

dominance: queen bees are covered in cuticular hydrocarbons that function as pheromones to inform others of their rank in the hive

Sexual Selection

a type of natural selection for successful mating

results in the reproductive advantage of some individuals over others of the same species/sex

remember fitness favors behaviors (innate or learned) that increase survival and reproduction

Mating Behaviors

animals can be monogamous or polygamous

Competition

males will compete for limited females

Courtship Rituals

help to ensure that the male/female are the same species

provides females opportunities to evaluate mates and/or signal for nest building and ovulation

Cooperation

many animals can benefit by forming groups

any behavior that benefits the group is known as cooperative behavior

cooperative behavior tends to increase fitness

ex. pack behavior: groups of animals coordinating activities, like hunting, leads to an increase in prey capture rate

ex. herd/flock behavior: reduces risk during migration, foraging, etc.

Altruism

selfless behavior, an individual behaves in a way that benefits others, but not itself

reduces the individual’s fitness, but increases the fitness of the rest of the population

ex. naked mole rat colonies have only one reproducing female (queen) who will only mate with a few males (kings). the other nonreproductive members will sacrifice themselves to protect their queen and kings