types of interactions
TRANSCRIPT
Types of Interactions
Look at the seaweed forest below. How many fish do you see? How
many seaweed plants do you count? Why do you think there are more
members of the seaweed population than members of the fish population?
Interactions with the Environment• Most living things produce
more living things than will survive
• A female frog may lay hundreds of eggs, but the population of frogs in a pond will stay about the same as it was the year before—Why?
• An organism interacts with biotic and abiotic factors that control the size of its population
Limiting Factors• Populations cannot
grow without stopping, because the environment contains a limited amount of food, water, living space, and other resources
• A resource that is so scarce that it limits the size of a population is called a limiting factor
• Any single resource can be a limiting factor to a population’s size
Carrying Capacity• Carrying capacity: largest population
that an environment can support• When a population is larger than its
carrying capacity, limiting factors cause individuals to die off or leave
• As individuals die or leave, the population decreases
• The population will return to a size that the environment can support
Interactions Between Organisms
• Four main ways that species and individuals affect each other:
CompetitionPredators and prey
Symbiotic relationshipscoevolution
Competition
• When 2 or more individuals or populations try to use the same resource, such as water, shelter, space, or light, it is called competition
• Can happen in populations or between populations
• Some trees grow tall to reach light, which reduces amt. available to short trees
Predators and Prey• Predator Adaptations
– To survive, predators have to be able to catch prey, using wide variety of methods and abilities
– Goldenrod spider ambushes its prey by blending in with flower and waiting for its insect meal to arrive
• Prey Adaptations– Prey have to keep from
being eaten– Are able to run away, stay
in groups, or camouflage themselves
– Some are poisonous– May advertise poison with
bright colors– Many small fishes swim in
groups called schools– Other animals stay in
herds, increasing the likelihood of spotting a potential predator
Camouflage
• One way to avoid being eaten is by being hard to see
• Blend in with the background
• May mimic twigs, leaves, stones, bark
Defensive Chemicals• Skunk and bombardier
beetle both spray predators with irritating chemicals
• Bees, ants, and wasps inject a powerful acid into their attackers
Bird called the hooded pitohui contains a deadly toxin—any predator that eats, or tries to eat, one of these animals will likely die
Warning Coloration• Predators will avoid any
animal that has the colors and patterns they associate with pain, illness, or unpleasant experiences
• Most common warning colors are
bright shades of red, yellow,
orange, black, and white
Symbiosis
• Symbiosis: a close, long term association between two or more species
• Individuals in a symbiotic relationship can benefit from, be unaffected by, or be harmed by the relationship
• Classified into 3 groups: mutualism, commensalism, and parasitism
Mutualism
• Mutualism both organisms benefit
• Example: corals and algae. Coral provide home for algae, algae produce food for the coral by photosynthesis
Commensalism• One organism benefits and the other is
unaffected• Example: relationship between sharks and
smaller fish called remoras. Remoras “hitch a ride” on sharks and feed on scraps of food left by sharks. The remoras benefit and sharks are unaffected.
Parasitism• One organism benefits while the other is harmed
• Organism that benefits is called the parasite, organism that is harmed is called the host
• Female wasp lays eggs on a tomato hornworm; eggs hatch, young burrow into caterpillar body, and actually eat the caterpillar alive! Then adult wasps fly away
Coevolution• When a long term
change takes place in two species because of their close interactions with one another, this change is called coevolution
• Ant and acacia tree ant protects tree and tree has special structures that make food for ants
Coevolution and Flowers• Flowers have changed over millions
of years to attract pollinators• Pollinators are attracted to color,
odor, or nectar• Flowers pollinated by
hummingbirds make nectar with the right amount of sugar for the bird
• Some bats changed over time to have long, thin tongues and noses to help them reach the nectar in flowers
• They help pollinate as they travel from flower to flower