Chapter 15

Question 1

What is a Symbiont?

Answer 1

organism that has entered into a long-standing and intimate relationship with an organism of another species

Question 2

What is Mutualism?

Answer 2

symbiotic relationship that occurs when both organisms are benefitted

Question 3

What is Commensalism?

Answer 3

symbiotic relationship where one organism benefits but the other is unaffected

Question 4

What is Parasitism?

Answer 4

symbiotic relationship where one organism benefits but the other is harmed

Question 5

What is a Pathogen?

Answer 5

microbe that routinely causes diseases in a host

Question 6

What is a Pathobiont?

Answer 6

lives as a symbiont with host as part of the microbiome but can potentially cause disease if the hosts condition changes

Question 7

What is Ectosymbionts?

Answer 7

live on the surface of host
EX: normal bacteria and yeast on skin, parasitic fungal species (athlete’s foot), Insect (fleas, ticks)

Question 8

What is an Endosymbionts?

Answer 8

live within the body of host and sometimes the host cells that have mutualistic or commensalism relationship

Question 9

What is an Endoparasites?

Answer 9

parasites that live within the body of the host and host cells and cause damage to the host such as the genus Plasmodium (malaria)

Question 10

What is a Lichen?

Answer 10

composite organism composed of a fungus and one or two photosynthetic algae or cyanobacteria

Question 11

What is a Mycobiont?

Answer 11

fungal organism of the Lichen

Question 12

What is a Photobiont?

Answer 12

Photosynthetic organism of the Lichen, sometimes two, mostly green algae, 10% cyanobacteria

Question 13

Benefits of lichens to organisms and vice versa

Answer 13

Allow both to grow in nutrient poor and inhospitable habitats EX: tree bark, rock
photobiont feeds mycobiont
mycobiont releases nutrients that the photobiont can feed off

Question 14

What are Endophytes?

Answer 14

plant endosymbionts, live within the tissue of plants

Question 15

What are Rhizobia?

Answer 15

Endophytes that infect plant root cells, fix nitrogen and form a root nodule

Question 16

How do root nodules form?

Answer 16

1. Bacterial nod genes are expressed in the presence of plants
2. flavenoids (compounds secreted by plants), induce the synthesis of nod factors, root curling
3. infection thread formed to invade the root
4. nodule forms providing a low oxygen environment

Question 17

What is bacteroid?

Answer 17

specialized cell type of an endosymbiotic nitrogen-fixing bacteria, helps in the formation of root nodules to protect from oxygen toxicity and high energy requirements