Starter: Discuss with a partner!   In Meagher’s Grant you’ll find populations of both wild rabbits and fox. Explain why there are usually more rabbits than fox (there are many reasons, how many can you come up with?).

  The following food web is an example of the interactions you can find in the Bay of Fundy. Herring is a popular fish to catch in this particular area. How would the “overfishing” of herring cause an increase in the population of sea urchins? Explain. Algae Aquatic plants Sea urchins Sea otters Sea Lions Herring Small fish

Which is density - independent population regulation?   Hurricane Juan   The eruption of Mount Vesuvius   Gang violence   Shortage of food   The Eastern shore of Nova Scotia being flooded in April   STDs

Which of the following are examples of intraspecific competition?   Shirley and Maria fighting over who gets to take Bob to the prom   The development of a swamp ecosystem for new condominiums in Gaetz Brook   My dog Toby growling at a cat over a place to sit   Children in war-torn Libya fighting over food

Which of the following are examples of biotic factors affecting a deer population?   The amount of grass in the forest   The amount of hunters in the forest   The amount of sunlight in the forest   The season (winter, summer, etc)   How much snow there is   The number of rivers in the forest

Ecology: Chapter 1.4 Productivity

Think About It…  Picture a field of vegetables growing in Nova Scotia, and a tropical rainforest in Guatemala.  Do you think a hectare of a Canadian field and a hectare of a tropical forest produce the same amount of biomass during a given period of time?  If not, what might make their production different?

Productivity of Ecosystems  Productivity: the average amounts of new plant biomass produced each year on a given area (kJ/m 2 /yr)  Different ecosystems have different productivities

Example 1: Estuary (where a river meets the sea) = kJ/m 2 /yr

Example 2: Tropical Rainforest = kJ/m 2 /yr

Example 3: Savanna (groves of trees with a grassy understory) = kJ/m 2 /yr

Example 4: Desert Scrub = kJ/m 2 /yr Example 4: Desert Scrub = kJ/m 2 /yr

Ecosystem Productivity Levels (See table, p. 25)  Estuary kJ/m 2 /yr  Swamp/Marsh kJ/m 2 /yr  Tropical Rainforest kJ/m 2 /yr  Temperate Forest kJ/m 2 /yr  Northern Coniferous Forest kJ/m 2 /yr  Savanna kJ/m 2 /yr  Agricultural Land kJ/m 2 /yr  Woodland and Shrubland kJ/m 2 /yr  Temperate Grassland kJ/m 2 /yr  Lakes and Streams kJ/m 2 /yr  Continental Shelf kJ/m 2 /yr  Open Ocean kJ/m 2 /yr  Tundra kJ/m 2 /yr  Desert Scrub kJ/m 2 /yr  Extreme Desert kJ/m 2 /yr

Productivity of different ecosystems:

Plant Productivity and Climate  Plant growth (and therefore land productivity) depends on:  Sunlight  Water (precipitation)  Carbon Dioxide  Nutrients such as nitrogen and phosphorus in the soil  Temperature  So, what’s the best climate for growth?

The Best Productivity  Warm temperature and wet areas = highest levels of productivity  Cooler temperature and little water = low levels of productivity  So why can’t we just irrigate a desert or clear a rainforest to grow crops?

 Replacing ecosystems can cause the loss of habitats for plants and animals, and a decrease in species diversity. This changes the energy flow if the ecosystem, change soil composition and cycling of water.

 It would be extremely costly to irrigate a desert and there would be many political issues as to where the water was coming from and which countries they would have to bring it from.

 Due to it’s high productivity, nutrients that are recycled back into the soil of a rainforest by the decomposers are used up as fast as they are replaced. As a result, if the rainforest is cut down and replaced by a less productive crop field, the very thin soil would soon be eroded away.

Desertification   One of the most serious problems facing people today is desertification.   It results from human activities that degrade the land and cause deserts to expand.   How much of Earth’s land surface do you think is affected by desertification? How many people are threatened by it?   What kinds of human activities contribute to desertification?   How can is be prevented?   Are there any regions in Canada that may be affected by this?