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UIC BioS 101 Nyberg

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CONSUMPTION
Herbivory, Predation and Parasitism

Organisms are a desirable resource for other organisms. In consumption one species increases in abundance (+) at the expense of another (-).

Speaker Notes:

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Infectious diseases are caused by organisms or viruses. Such diseases can be considered parasites.

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UIC BioS 101 Nyberg

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Reading Assignment

• The Reading for today’s lecture is Chapter 53, especially pages 1203-1207.

• Review of the disease lectures may be useful.

• Role of ‘quasi-species’ in disease is a new idea.

Speaker Notes:

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UIC BioS 101 Nyberg

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Herbivory, Parasitism and Predation

• Animals eating plants, herbivory, is a process distinguished from animals eating animals, predation, because 1) there is less action eating something that does not move, 2) consumption of animals normally kills the prey, but herbivory rarely kills the plant.

• Parasites are animals eating animals, but parasites are smaller than their host and do not normally kill the host.

Speaker Notes:

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An individual in which parasites or disease causing organisms live is called the host. Parasites generally do better if they do not kill the host.

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UIC BioS 101 Nyberg

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Herbivory

• Either roots or shoots eaten, not both.

• Animals consume plants as food, but plants clearly encourage the consumption of nectar (pollination) and fruits (disperse seeds).

• Plants have a variety of ways to defend themselves against being eaten including being hard to digest and toxin production.

Speaker Notes:

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Some animals eat above-ground leaves and others specialize on roots.

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UIC BioS 101 Nyberg

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Plant defenses against herbivores

• Prickles, spines and hairs.

• Compounds that taste bad and/or are harmful.

• Hard structures that make them difficult to consume (silica in grasses).

• Much of most plants is below ground, and takes a lot of energy to get to.

Speaker Notes:

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Red Queen Hypothesis

• The species being preyed upon has an advantage if it can evolve better defenses.

• The consumer does better (is more fit) if it can evolve ways of getting around the defenses.

• This leads to an evolutionary ‘arms race’ also know as the ‘red queen’ hypothesis.

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UIC BioS 101 Nyberg

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Speaker Notes:

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UIC BioS 101 Nyberg

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Overgrazed Pastures

• Animals can destroy all the vegetation in a habitat, but only do so when confined to a small area.

• Too high a stocking rate of grazers will reduce the potential of vegetation to provide nourishment in the future.

• Grazing is managed to maintain the future productivity of the land.

Speaker Notes:

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The capacity of animals, but not plants, to move seems to play are large role in understanding why the world is green.

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Why is the World green?

• Top-down model: Herbivore limited by predators

• Poor nutrition model: animals can’t grow fast enough on hard-to-digest food

• Plant defense model: plants aren’t all eaten because they protect themselves

• Landscape model: Animals move to more favorable patch before present patch gone.

Speaker Notes:

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UIC BioS 101 Nyberg

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Using defensive compounds to one’s own advantage

• Milkweeds produce a poison that stops many herbivores from eating the plant.

• Monarch butterfly caterpillars not only have overcome the negative effects of this poison, they store the poison in their own body and it protects the butterfly from birds.

• Bright colors often signify ‘poison’.

Speaker Notes:

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Black, yellow and white combine to suggest ‘danger’.

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UIC BioS 101 Nyberg

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Parasitism and Disease

• Infectious diseases are caused by viruses or organisms.

• The disease causing organism must be able to find a host (colonization) and then successfully overcome host defenses.

• From point of view of disease organism, infected and uninfected hosts are a metapopulation.

Speaker Notes:

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These definitions were given previously.

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UIC BioS 101 Nyberg

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Malaria as a parasite

• A protista, Plasmodium, that infects two hosts

  • Humans

  • Mosquitoes

• Multiple morphological forms in both hosts

• Multiple defenses are known in humans

  • Sickle cell allele of beta hemoglobin

  • HLA-B53 individuals with this allele display a protein on cell surface that causes other cells to kill that cell.

Speaker Notes:

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For multicellular hosts traits (such as HLA-B53) that make a cell more sensitive to infection help the entire host to survive longer. The same principle applies to a rust (fungus) that infects wheat.

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UIC BioS 101 Nyberg

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The immune system is our major defense against disease organisms. The immune system has many components including antibodies and cytotoxic cells. Diseases have evolved ways to quickly change surface proteins (changing more rapidly than the defense can respond) or make proteins that are not efficiently detected.

The most dangerous diseases of humans are often new diseases (mutations that allow animal diseases to infect humans).

How do individuals defend themselves

Speaker Notes:

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Quasi-species

• A new concept of viral diseases looks at the virus not as a genotype but rather as a population of genotypes.

• The virus has a high mutation rate and it needs the variation generated by mutation to effectively colonize diverse tissues.

Speaker Notes:

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A 2006 paper in Nature presented evidence of the quasi-species concept.

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Meta-analysis

• Studies which make observations and measurements of the natural world are called primary research

• Studies of models are called theoretical research

• Studies of primary studies, looking for consistent patterns are known as ‘meta-analysis’

Speaker Notes:

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Parasites may manipulate the host

• Infected individuals may behave differently than uninfected ones.

• If the altered behavior benefits the parasite, we say the parasite manipulated the host.

• Flatworm presence results in snail behavior that increases risk snail will be eaten by hawk which is next host in a complex life cycle.

Speaker Notes:

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Flukes in snail affect its behavior

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UIC BioS 101 Nyberg

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Speaker Notes:

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Predation

• Organisms are a rich source of material and food for other organisms.

• Predators are fast and powerful with good senses of a wide environment, but they have low abundances.

• Prey defend themselves in diverse ways.

Speaker Notes:

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Including Camouflage

Speaker Notes:

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Mimicry

• Black, yellow and white – not a tasty sight.

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Inducible Defenses

• When the presence of predators results in changes in the prey characteristics, the defensive response of the prey is said to be inducible.

• The example discussed in the book is shell thickness in mussels.

• Plants respond to leaf damage by producing defensive compounds.

Speaker Notes:

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Capacities to respond are limited. People have selected against defensive compounds in breeding plants.

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UIC BioS 101 Nyberg

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Predator Control

• Humans have hunted animals for food for many years.

• Plant eating animals are a preferred food source of humans.

• Predators that eat the same animals as humans hunt are viewed as competitors.

• Control of predators has increased the abundance of many prey species, i.e., deer.

Speaker Notes:

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Control of carnivores has increased the population of voles, rabbits, deer and other herbivores.

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Vocabulary

• Herbivore

• Parasite

• Predator

• Disease

• Quasi-species

• Inducible defenses

• Camouflage

• Keystone species

• Meta-analysis

• Over-fishing

• Predator control

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