1. Interaction between Species
A closer look…

2. First, a review What is carrying capacity?
How big a population can get while still being supported, having enough resources
How can you increase carrying capacity?
Altering ecosystem so more space, energy, and resources are available
Altering behaviour

3. Humans and Carrying Capacity
Humans have altered the ecosystems that support us, so the carrying capacity is high
But, modern human societies are still subject to the ecological principle of carrying capacity
Human growth has rapidly accelerated over the past 400 years
With a current doubling time of less than 1 human lifetime

4. Carrying Capacity

5. Human Population Growth

6. Ecological Footprint
Def: an estimate of how much land and water required to support someone’s lifestyle
What is your ecological footprint?
Mine is 6

8. Interaction Among Species
Resources and abiotic factors are not the only influences on a population
Organisms interact with each other too!

9. Ecological Niche Species focus on
Surviving
Reproducing
They do not have jobs, but they do contribute a ‘role’
Provide benefits to the ecosystem
Def: the role an organism plays within its ecosystem (biotic and abiotic factors)

10. Ecological Niche Sample niches There are millions of spots on Earth
Regulation of a population (like insects)
Decomposition of dead matter
Cycling of matter
There are millions of spots on Earth
There are millions of niches too

11. Carnivorous Plants

12. Predation and Population Size#1
Predation and Population Size
Predators and prey influence one another in 2 ways
Bottom-up population regulation
Top-down population regulation

13. Bottom-up population regulation
Grasshoppers eat grass; shrews eat grasshoppers
Grass  Grasshopper  Shrew
If the grasshoppers eat too much grass, population could decrease due to lack of food
If the population of grasshoppers decreases, there is not enough food for shrews  their population decreases

14. Bottom-up population regulation
This is called… … because there is a shortage in the plant resource at the base of the food chain which affects animals in higher trophic levels

15. Top-down population regulation
Now consider this…
What if the population of rabbits increases?
With more rabbits to eat, coyote population increases
But with more coyotes eating rabbits, the rabbit population will decrease
This is top-down regulation because a higher (top) trophic level organism influences the population of a lower trophic level
(eventually the # of coyotes would decrease too)

16. Competition #2
As the population of a species increases, so does the competition for resources
Can limit population size
The more energy an organism spends competing, the less energy it has for growth and reproduction

17. Symbiosis #3
The interaction between members of 2 different species that live together in close association
3 types of symbiosis
Mutualism
Commensalism
Parasitism

18. Mutualism
Def: symbiotic relationship between 2 species where both benefit
Ex: clownfish and anemones
Clownfish feed on small invertebrates which could potentially harm the sea anemone
Fecal matter from the clownfish provides nutrients to the sea anemone
Clownfish is additionally protected from predators by the anemone's stinging cells (which the clownfish is immune to)

19. Commensalism
Def: a relationship which is beneficial to one organism and neutral to the other
Ex: a bird nesting in a tree
Ex: Spanish moss

20. Parasitism
Def: symbiotic relationship between 2 species where 1 organism (parasite) depends on another larger organism (host)
Frequently the parasite benefits at the host’s expense
These primitive fish attach to the bodies of native fish and feed on the fish's body fluids. This often leads to the death of the native fish. Species at risk in the Great Lakes include prized commercial and recreational species such as lake trout, salmon, rainbow trout (steelhead), whitefish, walleye and catfish.

21. Malaria
Caused by the protozoan Plasmodium (single celled animal) that completes part of its life cycle in humans and part in mosquitoes
the disease is transmitted via a bite from an infected female Anopheles mosquito, which introduces the organisms from its saliva into the person's circulatory system. In the blood, the protists travel to the liver to mature and reproduce. Malaria causes symptoms that typically include fever and headache, which in severe cases can progress to coma or death. The disease is widespread in tropical and subtropical regions in a broad band around the equator, including much of Sub-Saharan Africa, Asia, and the Americas

22. Brain Worm White-tailed deer aren’t affected
Brain-worm cycle successful
Other animals are very vulnerable
Moose disease
Sheep
Elk
Caribou
Worm lays eggs in brain
Eggs travel to lungs and hatch
Larval worms excreted
Eaten by slugs
Eaten by deer

23. Human Parasitism
A 28-year-old medical resident and a companion returned from hiking in Central America with lesions on their lower extremities
After learning that they had been walking barefoot on the beach during their vacation, they were diagnosed with cutaneous larva migrans
Hookworm eggs are shed in infected dog (or other animal) feces to the ground, where they then develop over a period of 1–2 weeks into the infectious larval form (filariform larvae).[3] The filariform larvae can burrow through intact skin that comes into contact with soil or sand that is contaminated with feces. Although they are able to infect the deeper tissues of animals (through to the lungs and then the intestinal tract), humans are incidental hosts and the larvae are only able to penetrate the upper dermis of the skin[1] and thus create the typical wormlike burrows visible underneath the skin. These parasites apparently lack the collagenase enzymes required to penetrate through the basement membrane deeper into the skin.
Cutaneous larva migrans (CLM) was first described as "the creeping eruption" in 1874
Today, it is one of the most common hookworm infections
acquired from subtropical and tropical regions of the world