among organisms

Generate stability within an ecosystemAre types of density-dependent limiting

factorsCompetitionPredationSymbiosis

CompetitionOrgs. of

same or diff. species want to use same resource @ same place/time

Competing for light, water, space, nutrients

CompetitionOrgs. of

same or diff. species want to use same resource @ same place/time

PredationOne org.

captures and feeds on another org.

Mud dauber wasps sting and paralyze spiders. They seal them in mud nests for their young to feed.

PredationOne org. captures

and feeds on another org.

Ladybeetle about to devour an aphid

PredationOne org. captures

and feeds on another org.

SymbiosisTwo sp. living closely together

Three types…

SymbiosisMutualism:Both orgs. benefit from each other(+/+)

SymbiosisMutualism:Both orgs. benefit from each other(+/+)

Clownfish are frequently found in the tentacles of sea anemones, which typically capture their prey by paralyzing them with discharged cnidoblasts (nematocysts) , and then ingesting the animal within the gastrovascular cavity. Studies have shown that a component of clownfish mucus inhibits the discharge of these cnidoblasts.

A remarkable 3-way mutualism appears to have evolved between an ant, a butterfly caterpillar, and an acacia in the American southwest. The caterpillars have nectar organs which the ants drink from, and the acacia tolerates the feeding caterpillars. The ants appear to provide some protection for both plant and caterpillar.

© Gregory G. and Mary Beth Dimijian

A fly agaric mushroom (Amanita muscaria) and a cone of Eastern White Pine are side by side on a New Hampshire forest floor in October. A sapling of Eastern Hemlock sends sprays over the mushroom, and wintergreen adds a splash of red. The pine and fungus form a partnership in which underground filaments of the mycorrhizal fungus invade the roots of the pine, and both provide essential nutrients to each other. Both partners have their reproductive structures above ground.

© Gregory G. and Mary Beth Dimijian

Tiny fig wasps reproduce inside unripe figs and can be seen if the fig is cut open at the right stage. These wasps and fig trees are "obligate mutualists," meaning that they cannot reproduce without each other. A parasite of the mutualism is seen in the inset, with a long ovipositor with which she lays her eggs inside the fig.

© Gregory G. and Mary Beth Dimijian

SymbiosisCommensalism:One species benefits, the other is neither helped or harmed.(+/0)

Barnacles on a gray whale

A critical phase in the life cycle of plants is the proper dispersal of its seeds. Many wonderful or strange adaptations have evolved to insure this dispersal. One of these adaptations is the evolution of recuved spines on the seeds or seedpods to attach the seeds to the fur of passing vertebrates who carry the seeds away from the parent plant. In the case of humans, fur is replaced by pants, sweaters, socks, and other pieces of clothing. Plants, therefore, anticipated the invention of velcro from several million years. The plant benefits from the relationship by the

dispersal of its seeds. The vertebrates are not affected except, perhaps, by being annoyed.One of the most famous examples are the burdocks, common weeds found along roadsides and in empty lots and fields. The species on the left is the Great Burdock (Arctium lappa). The seed heads (burs) of burdocks long spines with hooked tips. The hooked tips catch onto the hair of passing vertebrates (cows, deer, dogs, humans) and the burs are carried elsewhere until they finally drop off or are pulled off by the carriers.

The Monarch butterfly (Danaus plexippus) feeds as a larva on species of milkweeds (Asclepias spp.). The milkweeds contain a group of chemicals called cardiac glycosides. Cardiac glycosides are poisonous to vertebrates (although not to invertebrates). The larvae store these cardiac glycosides and the later adult contains them as well. If a bird (or other vertebrate such as a mouse or frog) eats a Monarch it finds them distasteful to begin with and is later sick. Experimentally birds learn to avoid Monarchs. The Monarch advertises its inedibility by a bright orange and black coloration.The Viceroy (Limentis archippus) is not distasteful and does not contain cardiac glycosides. However by mimicing the the pattern of the Monarch it is also avoided by birds and other vertebrates that have learned to avoid the Monarch. This particular relationship is called Batesian Mimicry.

The Demodicid

Demodex folliculorium

< 0.4mm longLives in pores and hair follicles, usually on the nose, forehead, cheek, chin, and in roots of eyelashes

The Demodicid

Demodex

folliculorium

Live head down,

feeding on

secretions and

dead skin.

Can lay 25 eggs.

They grow, leave

to mate and find

other follicles.

SymbiosisParasitism:One species lives on or in its host, harming it. (+/-)

A tomato hornworm is covered with cocoons of pupating braconid wasps.

Pediculus humanus (head louse) adult.

Dirofilaria immitisdog heartworm

Adult Rhodnius prolixus taking a blood meal through human skin. The reduviid insect transmits the parasites which cause Chagas disease in feces deposited near the site of their bite. Scratching or rubbing by the person bitten can transfer the parasites into the body via the wound or other sites such as the eye.

Human tapeworm

tapeworm

Sheep tapewormHead – called scolexBody segments – proglottidsEach body segment

has ovaries and testes(hermaphroditic)

Each segment can reproduce another worm (called gravid [fertile])