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Photo (a) shows yellow termites and photo. (b) shows a tree covered with lichen.
(a) Termites form a mutualistic relationship with symbiotic protozoa in their guts, which allow both organisms to obtain energy from the cellulose the termite consumes. (b) Lichen is a fungus that has symbiotic photosynthetic algae living inside its cells. (credit a: modification of work by Scott Bauer, USDA; credit b: modification of work by Cory Zanker)

Parasitism

A parasite    is an organism that lives in or on another living organism and derives nutrients from it. In this relationship, the parasite benefits, but the organism being fed upon, the host    is harmed. The host is usually weakened by the parasite as it siphons resources the host would normally use to maintain itself. The parasite, however, is unlikely to kill the host, especially not quickly, because this would allow no time for the organism to complete its reproductive cycle by spreading to another host.

The reproductive cycles of parasites are often very complex, sometimes requiring more than one host species. A tapeworm is a parasite that causes disease in humans when contaminated, undercooked meat such as pork, fish, or beef is consumed ( [link] ). The tapeworm can live inside the intestine of the host for several years, benefiting from the food the host is bringing into its gut by eating, and may grow to be over 50 ft long by adding segments. The parasite moves from species to species in a cycle, making two hosts necessary to complete its life cycle. Another common parasite is Plasmodium falciparum , the protozoan cause of malaria, a significant disease in many parts of the world. Living in human liver and red blood cells, the organism reproduces asexually in the gut of blood-feeding mosquitoes to complete its life cycle. Thus malaria is spread from human to human by mosquitoes, one of many arthropod-borne infectious diseases.

The life cycle of a tapeworm begins when eggs or tapeworm segments in the feces are ingested by pigs or humans. The embryos hatch, penetrate the intestinal wall, and circulate to the musculature in both pigs and humans. Humans may acquire a tapeworm infection by ingesting raw or undercooked meat. Infection may results in cysts in the musculature, or in tapeworms in the intestine. Tapeworms attach themselves to the intestine via a hook-like structure called the scolex. Tapeworm segments and eggs are excreted in the feces, completing the cycle.
This diagram shows the life cycle of a pork tapeworm ( Taenia solium ), a human worm parasite. (credit: modification of work by CDC)

Characteristics of communities

Communities are complex entities that can be characterized by their structure (the types and numbers of species present) and dynamics (how communities change over time). Understanding community structure and dynamics enables community ecologists to manage ecosystems more effectively.

Foundation species

Foundation species are considered the “base” or “bedrock” of a community, having the greatest influence on its overall structure. They are usually the primary producers: organisms that bring most of the energy into the community. Kelp, brown algae, is a foundation species, forming the basis of the kelp forests off the coast of California.

Foundation species may physically modify the environment to produce and maintain habitats that benefit the other organisms that use them. An example is the photosynthetic corals of the coral reef ( [link] ). Corals themselves are not photosynthetic, but harbor symbionts within their body tissues (dinoflagellates called zooxanthellae) that perform photosynthesis; this is another example of a mutualism. The exoskeletons of living and dead coral make up most of the reef structure, which protects many other species from waves and ocean currents.

Questions & Answers

what is nutrients
Patrick Reply
what are the types of skeleton
Tanyi Reply
endo skeleton and exo skeleton
Faith
or types of skeletons There is exo skeleton found in class insecta Exo skeleton found in phylum chordata and lastly hydrostatic skeleton found mainly in earth worms
Daniel
and hydrostatic skeleton
Godbless
what is life?
Jerson Reply
life is when any living thing breath or respirate.
Lucky
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Patrick
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Monday
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Yahaya
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Lucky
give an example of a phylum where all members have open circulatory
Omoro Reply
anthropoda
Daniel
phylum Anthropoda
Daniel
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Maggie
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create employment
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pollution
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pollution and lack of knowledge about how to manage waste
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what is gametophyte
Ibrahim Reply
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Basiru Reply
Biology deals with the study of living organisms and their interactions with each other and the environment.
Quartey
biology simply means the study of living and non-livingthings.
Shamstar
what is the meaning of ubiquitous
Hamziyatu Reply
Under what topic is this question
fred
three branches of biology
Alexander Reply
what is the cell
Olajide Reply
what is life
Olajide
cell is the functional and structural unit of life
Shweta
life is a problem solving entity
Atanga
what is the characteristics of plant cell
Quaku
Describe the process that results in the formation of a tetrad.
Michael Reply
what is biology
Ndukwe Reply
biology is the study of life
Oghenemine
what is biology
Jimmy Reply
the study of life
Hamziyatu
what is the Biosphere?
Kabel Reply
I want to know what classifications of living organisms and their names
Quaku
are classified into plants and animals eukaryotic and prokaryotic cell.
Lokwe
what is biology?
Turabi Reply
what is the meaning of Biologists
Turabi
what is the meaning of Biologists
Turabi
what is the meaning of Biologists
Turabi
are those who are specialized in Biology
Nicode
Is the study of living things,
Kabel
what is the ecosystem?
Kabel
bio mean life logus means study so the study of living things or living organisms is called biology
Faraq
Ecosystem consists of the living organisms in a particular area together with the abiotic factors.
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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