Predation

Question 1

Give examples of major components of snake venom.

Answer 1

Phospholipases- Break ester bonds in phospholipids. Proteases - Break up protein at links between amino acids. Phosphatases - Fragment ATP. Hyaluronidases- Break up extracellular materials. Neurotoxins - Bind strongly to receptor molecules that receive chemical messages from neurons causing paralysis.

Question 2

Identify two similarities in the predation strategy of non-constricting snakes and orb web spiders.

Answer 2

Both sit and wait for prey and both use toxins.

Question 3

What selective advantage to plants is gained by the possession of neurotoxins?

Answer 3

They will deter potential herbivores.

Question 4

What is the key to understanding neurotoxins?

Answer 4

The key to understanding the action of neurotoxins lies in their structural similarity to neurotransmitters, which include acetylcholine, dopamine, noradrenalin and serotonin. Neurotransmitters are molecules that either pass across the gaps (synapses) between nerve cells (neurons) or across synapses between a neuron and muscle – the neuromuscular junction.

Question 5

Summarise the main features of large cats which make them particularly adept predators.

Answer 5

Features include: retractable claws, powerful jaws and large teeth, agility and rapid movement and, in some cases, social organisation (hunting in packs).

Question 6

What animals are in the clade Carnivora and what do they eat?

Answer 6

cats, dogs, bears. Animals, often other mammals.

Question 7

What animals are in the clade Eulipotyphla and what do they eat?

Answer 7

shrews, moles, hedgehogs - they eat invertebrates.

Question 8

What animals are in the clade Cetartiodactyla and what do they eat?

Answer 8

whales, hippopotamus, pigs they eat plants and animals (omnivorous)

Question 9

What animals are in the clade Afrotheria and what do they eat?

Answer 9

golden moles, aardvarks, elephants they eat plants and invertebrates

Question 10

Define ecological community.

Answer 10

A set of interacting organisms in one location, which may include plants, herbivores, other predators and parasites.

Question 11

What is the distinction between an ecological community and an ecosystem?

Answer 11

The former refers to all the living (biotic) components whereas the latter also includes non-living (abiotic) components.

Question 12

Apart from direct observations of predators taking prey or the remains of carcasses with characteristic bite marks, how can you tell what predators are eating?

Answer 12

Stable isotope analysis gives information on types of diet. Specifically, for mammals the isotope ratio of 12C and 13C in tooth enamel gives information on whether the diet was primarily herbivore or carnivore.

Question 13

Summarise the methodological options available to an ecologist who wishes to examine the role of competition and predation in structuring an intertidal community.

Answer 13

Undertake a field experiment involving the removal (or possibly addition) of species from one or more study sites. Undertake a laboratory or microcosm experiment targeted at a few of the species (this may not be as informative as the field experiment as complex trophic interactions may be missed). Develop a mathematical model of the interactions.

Question 14

Define allometry.

Answer 14

Changes in organism function (e.g. physiology) with body size.

Question 15

What is the allometric relationship between basal metabolic rate and body mass?

Answer 15

BMR = 70m to the power 0.75. Therefore BMR for an animal can be predicted from its mass to the power 0.75, multiplied by 70.

Question 16

What are the two categories of predators?

Answer 16

Predators fall into two broad categories: those that chase their prey and those that wait for their prey. These different categories of predation result in different selection pressures for both predators and the prey.

Question 17

Summarise findings on the relationship between predator and prey size. What is the crucial weight at which predator-prey mass interactions alters?

Answer 17

22kg. Predators below 22kg generally feed on prey less than 45% their own body mass (cat & mouse). Predators over 22kg generally feed on prey over 45% their body mass (lion and wildebeest)

Question 18

How is Batesian or Müllerian mimicry related to interactions between predators and prey?

Answer 18

Both of these forms of mimicry involve the use of warning colouration by prey against potential predators.

Question 19

What is the best way to determine if coevolution is occurring?

Answer 19

The best way to determine whether coevolution is occurring is to compare the phylogenies of the two clades involved. It is predicted that the rate and type of change in one of the coevolving clades will be mirrored by change in the other, so phylogenies should look similar.

Question 20

What statistical tests are used to determine the difference between two sets of data (and whether the null hypothesis can be accepted or rejected)?

Answer 20

The Mann–Whitney U-test and the t-test

Question 21

What is a trophic cascade?

Answer 21

The interconnections between species provide opportunities for trophic cascades, in which species in one trophic level may be radically affected by the increase or decrease of species at another trophic level. These ideas can be tested in the field with removal experiments.

Question 22

What effect are domestic cats having on urban Eco systems?

Answer 22

Predation by domestic cats may be high in suburban areas and potentially affect a wide range of prey. A small proportion of cats, generally the younger ones, are responsible for a high proportion of predation.

Question 23

What example of coevolution exists among felines?

Answer 23

Strong evidence for coevolution exists between cat species and their parasites. The evidence is based on the similarity of phylogenies, which can be tested statistically by correlating nucleotide substitution rates in the two groups. Particularly their papillomaviruses.