Lecture 18

Question 1

Symbiosis

Answer 1

Relationship between two or more organisms that live together

• Mutualism
• Commensalism
• Parasitism

Question 2

Mutualism

Answer 2

Where both species benefit from the relationship

Question 3

Commensalism

Answer 3

Where one species benefits, while the other is neither harmed nor helped

Question 4

Parasitism

Answer 4

Where one member of the relationship is harmed in the process

Question 5

Horizontal transmission

Answer 5

Host reproduction leads to symbiotic- free descendents, which at a certain life stage are infected with symbionts from the environment

Question 6

Vertical transmission

Answer 6

(usually maternal) Prior to host reproduction symbionts are translocated to the female gonads, resulting in symbiotic descendants

Question 7

Obligate or primary symbionts

Answer 7

Essential for host survival and reproduction, and are often housed in special organs inside the insect called the bacteriome

Question 8

Facultative or secondary symbionts

Answer 8

– Within a host species, there is variation in whether a particular secondary symbiont is found in an individual
– May have a much broader array of effects, including defence against natural enemies, reproductive manipulation, environmental adaptation and host nutrition

Question 9

Indirect impacts of insect symbionts on plant communities

Answer 9

When symbionts between the two are exchanged, the feeding pattern is reversed, hence symbionts can impact plant community ecology indirectly

Question 10

Reproductive manipulators

Answer 10

Since symbionts are often maternally transmitted, any strategy favouring infected matrilines will spread the infection

Question 11

Two broad categories of reproduction manipulation

Answer 11

1. Induction of female-biased sex ratios

2. Reduction of female production by uninfected females through cytoplasmic incompatibility (CI)

Question 12

Parthenogenesis

Answer 12

reproduction and growth of embryos without fertilization