Lec 13

Question 1

Symbiotic Relationship

Answer 1

Very close associations between individuals of two species in which one lives on or in the other and both are physiologically integrated to some extent
–Biologically intertwined; KEY to symbiosis

Question 2

NON-symbiotic Relationships

Answer 2

Do NOT involve any physiological integration

–Competition/Amensalism, True predation/herbivory

Question 3

Competition, amensalism, and true predation/herbivory are _____________ relationships

Answer 3

non-symbiotic

Question 4

Parasitism and mutualism are often, but not always, ____________

Answer 4

Symbiotic

Question 5

Commensalism is usually ____________

Answer 5

Non-symbiotic

Question 6

Parasite

Answer 6

An organism that livesin close association with a host organism

The parasite depends on the host for its nutrition and other resources (shelter, reproduction)

In the process, the parasite harms the host but generally does not kill it

If the host dies, so too will the parasite

Over time, the host often does die, and the parasite dies as well
–By this point, the parasite has completed reproduction and potentially produced many offspring

Parasite species are very specific to only certain host species

Question 7

Types of Parasites

Answer 7

Certain species within all major groups of oranisms act as parasites:

• Bacteria
• –NO parasitic archaea known; could just say “prokaryotes” (more broad, includes bacteria and archaea) to eliminate problem of “all major groups”
• Fungi
• Viruses
• Protists (protozoans, water mold (caused potato famine)
• Animals (worms, arthropods)
• Plants (dodder, mistletoe)

Question 8

Microparasites

Answer 8

Small (microscopic)

Bacteria, viruses, protozoans, such as Plasmodium

Question 9

Macroparasites

Answer 9

Large (macroscopic)

Tapeworms, fleas, lice

Question 10

Endoparasites

Answer 10

Live and reproduce within their host

Often microparasites (bacteria, protozoans)

SOME macroparasites (worms)

SYMBIOTIC
–Physiological integration is certainly involved (i.e. immune response by host)

Question 11

Ectoparasites

Answer 11

Live and reproduce on the outside of their host

Often macroparasites (ticks, mites, fleas, lice, fungi)

SOME microparasites as well

NONSYMBIOTIC
–No physiological integration (i.e. ticks can go b/w hosts before causing any response)

Question 12

Obligatory parasites

Answer 12

Die if their host dies

MOST parasites are obligatory

Question 13

Facultative parasites

Answer 13

Continue to live even if the host dies

SOME fungi kill their host trees but then continue decomposing them afterwards

Question 14

Parasite Life Cycles

Answer 14

VERY complex

Involve sexual and asexual reproduction

Involve 2 or more alternate hosts

• -ALTERNATE, NOT alternative
• –Must go in a specific sequence between hosts, can’t just “choose” whichever is available

Sexual reproduction occurs in the DEFINITIVE (primary) host

Asexual reproduction occurs in the INTERMEDIATE (secondary) host

Question 15

Life Cycle of Plasmodium

Answer 15

Plasmodium: Unicellular protozoan that causes malaria

A mosquito injects Plasmodium (in its sporozoite stage) into a human’s blood while feeding

Sporozoites penetrate into human liver cells, where they divide asexually into the merozoite stage
–Daughter cells as product of MITOSIS (same ploidy level before and after; n -> n in this case (haploid to haploid))

Merozoites infect human red blood cells, where they continue to divide (asexually) and multiply

Merozoites lyse (break out of) the red blood cells, causing the fevers and chills associated with malaria

Some merozoites infect more red blood cells, while others develop into gametocytes

Gametocytes are ingested with the blood by a new mosquito when the human is fed upon again

Within the mosquito, the gametocytes act as gametes, fertilizing each other to form a zygote

The zygote is the ONLY DIPLOID stage in the Plasmodium life cycle

Zygote immediately undergoes MEIOSIS (change ploidy levels; 2n -> n in this case (diploid to haploid)) to produce sporozoites

The sporozoites migrate to the mosquito’s salivary glands

Sporozoites are injected into another human when the mosquito feeds again, starting the life cycle over

The mosquito if the DEFINITIVE host
–Where Plasmodium undergoes fertilization and meiosis

The human is the INTERMEDIATE host
–Where Plasmodium undergoes mitosis

Plasmodium is PHYSIOLOGICALLY INTEGRATED and therefore involved in a symbiotic relationship, with both of its hosts

Plasmodium induces mosquitoes to become more bloodthirsty

The human immune system is constantly working to attack Plasmodium

The parasite/host relationship is very specific

There are many species within the genus Plasmodium, but only a few infect humans

Only female mosquitoes within the genus Anopheles are infected

Question 16

Ecological Effects of Parasites

Answer 16

Parasites can reduce the range of host populations, or drive them extinct altogether

Prior to 1900, the American chestnut tree (Castanea dentata) was dominant throughout the forests of the eastern United States

In 1904, the fungus Cryphonectria parasitica was accidentally introduced into NYC from China

By 1930, nearly all of the 3.5 billion chestnut trees had died due to blight caused by the fungus

Though the chestnut tree is not extinct, the composition of forests in the eastern US is entirely different today

Question 17

Brood Parasitism

Answer 17

One egg-laying species (the “parasite”) has another egg-laying species (the “host”) raise its offspring

The parasite species benefits by outsourcing parental cure of their young

The host species is harmed by squandering energy on unrelated individuals

Most PREVALENT in birds, also present in fish