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 Ecology: Chapter 1.4 Productivity1.4 Productivity

Think About It…Think About It… Picture a field of vegetables Picture a field of vegetables

growing in Nova Scotia, and a growing in Nova Scotia, and a tropical rainforest in Guatemala.tropical rainforest in Guatemala.

Do you think a hectare of a Do you think a hectare of a Canadian field and a hectare of Canadian field and a hectare of a tropical forest produce the a tropical forest produce the same amount of biomass during same amount of biomass during a given period of time?a given period of time?

If not, what might make their If not, what might make their production different?production different?

Productivity of Productivity of EcosystemsEcosystems ProductivityProductivity: the average : the average

amounts of new plant biomass amounts of new plant biomass produced each year on a produced each year on a given area (kJ/mgiven area (kJ/m22/yr)/yr)

Different ecosystems have Different ecosystems have different productivitiesdifferent productivities

Example 1: Estuary (where a Example 1: Estuary (where a river meets the sea) = 40 000 river meets the sea) = 40 000 kJ/mkJ/m22/yr/yr

Example 2: Tropical Rainforest = Example 2: Tropical Rainforest = 40 000 kJ/m40 000 kJ/m22/yr/yr

Example 3: Savanna (groves of Example 3: Savanna (groves of trees with a grassy understory) = trees with a grassy understory) = 13 000 kJ/m13 000 kJ/m22/yr/yr

Example 4: Desert Scrub = 2 Example 4: Desert Scrub = 2 000 kJ/m000 kJ/m22/yr/yr

Ecosystem Productivity Ecosystem Productivity Levels (See table, p. 25)Levels (See table, p. 25)

EstuaryEstuary 40 000 40 000 kJ/mkJ/m22/yr/yr Swamp/MarshSwamp/Marsh 40 000 40 000 kJ/mkJ/m22/yr/yr Tropical RainforestTropical Rainforest 40 000 40 000 kJ/mkJ/m22/yr/yr Temperate ForestTemperate Forest 25 000 25 000 kJ/mkJ/m22/yr/yr Northern Coniferous ForestNorthern Coniferous Forest 15 000 15 000 kJ/mkJ/m22/yr/yr SavannaSavanna 13 000 13 000 kJ/mkJ/m22/yr/yr Agricultural LandAgricultural Land 12 500 12 500 kJ/mkJ/m22/yr/yr Woodland and ShrublandWoodland and Shrubland 12 000 12 000 kJ/mkJ/m22/yr/yr Temperate GrasslandTemperate Grassland 10 000 10 000 kJ/mkJ/m22/yr/yr Lakes and StreamsLakes and Streams 10 000 10 000 kJ/mkJ/m22/yr/yr Continental ShelfContinental Shelf 7 000 7 000 kJ/mkJ/m22/yr/yr Open OceanOpen Ocean 5 000 5 000 kJ/mkJ/m22/yr/yr TundraTundra 3 500 3 500 kJ/mkJ/m22/yr/yr Desert ScrubDesert Scrub 2 000 2 000 kJ/mkJ/m22/yr/yr Extreme DesertExtreme Desert 1 000 1 000 kJ/mkJ/m22/yr/yr

Productivity of different ecosystems:

Plant Productivity and ClimatePlant Productivity and Climate

Plant growth (and therefore land Plant growth (and therefore land productivity) depends on:productivity) depends on: SunlightSunlight Water (precipitation)Water (precipitation) Carbon DioxideCarbon Dioxide Nutrients such as nitrogen and Nutrients such as nitrogen and

phosphorus in the soilphosphorus in the soil TemperatureTemperature

So, what’s the best climate for So, what’s the best climate for growth? growth?

The Best ProductivityThe Best Productivity

Warm temperature and wet Warm temperature and wet areas = highest levels of areas = highest levels of productivityproductivity

Cooler temperature and little Cooler temperature and little water = low levels of water = low levels of productivityproductivity

So why can’t we just irrigate a So why can’t we just irrigate a desert or clear a rainforest to desert or clear a rainforest to grow crops?grow crops?

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

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

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