E7

Question 1

What is predation?

Answer 1

Consumption of one organism by another organism in which the prey is alive and attacked by the predator. This excludes detritivory (consumption of dead matter).

Question 2

What percentage of species obtain energy by feeding on other organisms?

Answer 2

> 50%. All = exploitation = one organism benefits by feeding on, thus directly harming another.

Question 3

What are the three levels of taxonomic classification?

Answer 3

Carnivores consume animals
Herbivores consume plants
Omnivores consume from both trophic levels

Question 4

What are the four levels of functional classification?

Answer 4

True predators, grazers, parasitoids, parasites.

Question 5

What do true predators do?

Answer 5

Kill prey immediately after attack. May kill and consume many different prey types or individuals.

Question 6

What do grazers do?

Answer 6

Attack large amounts of prey, but only remove a part of each prey individual. Harmful but rarely lethal.

Question 7

What do parasites do?

Answer 7

Consume parts of their prey, harmful but rarely lethal in the short term. An intimacy of association, only one or a few hosts in a lifetime. Tapeworm, liver fluke, plant galls. Also plants,

Question 8

What do parasitoids do?

Answer 8

A group of insects, mainly Hymenoptera. Free-living adults lay eggs in/on other hosts. Larvae live within host until they emerge and destroy host. 10% of worlds species

Question 9

What are some traits of true predators?

Answer 9

Broad diets, forage throughout habitat for food. Others sit-and-wait predators, remain in one place and attack prey that move within striking distance or enter trap. Some predators forage on most abundant prey, switching may occur because the predator forms a search image of the most common pret type and orients towards the prey. Or learning enables them to become proficient at capturing this prey.

Question 10

What are some traits of herbivores?

Answer 10

Specialises on one tupe of plant part, most commonly leaves. Feed on narrow range of plants species

Question 11

What are some adaptations for predation?

Answer 11

Life changed radically with appearance of the first macroscopic predators roughly 530 millions years ago. Before that the seas were dominated by soft-bodied organisms. Prey develop defences. Predators exert strong selection pressure on their prey if prey are not defended well they die. Physical defences or toxins or aposematic warnings.

Question 12

What are some tradeoffs between behavioural and physical defences?

Answer 12

Snail defence to crabs either thick shells or detection of crab odours.

Question 13

How do plants respond to herbivores selection pressures?

Answer 13

Avoidance, tolerance, defences.

Question 14

What is avoidance?

Answer 14

Avoidance on a large time scale some produce huge numbers of seeds in some years and hardly any in other years. Plants hide from seed eating herbivores then overwhelm them by sheer numbers. Avoidance on a short time scale producing leaves at times of the year when herbivores are scarce.

Question 15

What is tolerance?

Answer 15

Tolerance - compensation growth responses that allow the plant to compensate for herbivory. Removal of plant tissue stimulates new growth. Removal of leaves can decrease self shading resulting in increased plant growth. Removing of apical buds may allow lower buds to open and grow. For some plants herbivory can be a benefit in some circumstances, herbivory early in the growing season results in compensation.

Question 16

What are defences?

Answer 16

Plants have an array of structural defences, spines, thorns, hairs that pierce the skin. Secondary compounds are chemicals that reduce herbivory, some are toxic, others attract predators or parasitoids that will attack herbivores. Induced defences are stimulated by herbivore attack. E.g. cacti increase spine production.

Question 17

What defences do tobacco plants have?

Answer 17

Toxic secondary compound that deter herbivores directly, compound that deter herbivores indirectly by attracting predators and parasitoids. Kessler et al used gene silencing to develop three varieties in which one of the three genes was disabled. Three genes are a part of a chemical pathway thought to control the induction of both direct (toxins) and indirect (attractants) defences. Lox3 gene implicated in defences, therefore results showed that changes in a single gene can alter both the level of herbivory and the community of herbivores. It also showed the power of combining the molecular genetic techniques with ecological field experiments and being able to examine the effects of particular genes in a natural setting.

Question 18

What does improvement of defence adaptations do? And how have predators adapted?

Answer 18

Exerts pressure on predators and herbivores. For any defence mechanism there is usually a predator with a countervailing offense. Cryptic prey may be detected by smell, some predators subdue prey with poisons, some use mimicry, blending into environment so prey are unaware of presence. Some have inducible traits (ciliate that adjust size to match the size of available prey. Some predators detoxify or tolerate prey chemical defences. Plant defences can also be overcome by herbivores. Many have digestive enzymes that allow them to tolerate plant toxins, this can provide an abundant food source that other herbivores cannot exploit. Some plants produce toxic sticky resins and store them in canals in leaves and stems.

Question 19

What is the fear factor - lynx and snowshoe hare as a case study?

Answer 19

Abundance of lynx and snowshoe hates cycles, what drives fluctuations in hare pops, hare pops rise and fall in synchrony across broad regions of Canada. Experiment looking at blocks of forest in Canada, food was added to two blocks, electric fence used to exclude predators from one, one block had added food and no predators, survival rates and densities of hares in each block were monitored for an 8 year period. Compared with controls, hare densities high in all three treatments. Pop studies showed that hare reproductive rates reached highest levels several years before hare density reached maximum. Then they decrease, reaching the lowest levels 2-3 yrs post hare density peak. Role of prey fear also plays a role greater than actual impact of lynx.

Question 20

How do predation and herbivory affect ecological communities?

Answer 20

Cause a shift from one community type to another. All exploitative interactions have the potential to reduce growth, survival, or reproduction of organisms that are eaten. E.g. lesser snow geese can benefit salt marshes of Canada where they fertilise the nitrogen poor soil with faeces. Plants then grow rapidly. Then lesser snow geese density rose exponentially and at high densities the geese completed removed vegetation drastically changing the distribution and abundance of marsh plant species.

Question 21

What are saprotrophs?

Answer 21

Organisms that make use of dead organic matter. Do not control the rate of availability of resources. Dependent on rate of another force. Decomposers (bacteria and fungi), detritivores (animal consumers of dead matter)

Question 22

What are decomposers?

Answer 22

Break down dead matter (not predation). Can include plant matter and animal waste as well as dead bodies. Release of energy and mineral nutrients. Complex organic molecules are broken down to yield CO2, water and inorganic nutrients. Lower activity in low temperatures, poor aeration, scarce soil water and acidic conditions.

Question 23

What are detritivores?

Answer 23

Consume dead matter, taxonomically diverse group, in terrestrial environments classified according to size. Some animal communities are composed exclusively of detritivores e.g. forest floor. Recycling of organic matter, very important ecosystem service providers.