Everything Life Sciences Grade 10

FACT

WATCH:Bill Nye

the science guy

talks about the food

web:

See video:

SHORTCODEat

http://www.everythingscience.co.za

FACT

WATCH:A simple

video explaining

nutrient cycling:

See video:

SHORTCODEat

http://www.everythingscience.co.za

Textbook

Instructions:

Look at the food web and the diagram showing the different trophic levels.

Questions:

1. Identify a food chain that has three trophic levels.


2. Identify a food chain that has four trophic levels.


3. Name 2:
   a) Producers
   b) Primary consumers
   c) Secondary consumers
   d) Tertiary consumers


4. There are very few tertiary consumers compared to the primary consumers. Why?


5. What will happen if the hyena is removed from the food web?

9.7 Nutrient cycles

Anutrient cycle refers to the movement and exchange of organic and inorganic matter back
into the production of living matter. The process is regulated by the food web pathways
previously presented, which decompose organic matter into inorganic nutrients. Nutrient
cycles occur within ecosystems. Nutrient cycles that we will examine in this section include
water, carbon, oxygen and nitrogen cycles.

Water cycle DUMMY

Over two thirds of the earth’s surface is covered by water. It forms an important component
of most life forms, with up to 70% of plants and animals being composed of water. Vast
quantities of water cycle through Earth’s atmosphere, oceans, land and biosphere. This
cycling of water is called thewater or hydrologicalcycle. The cycling of water is important
in determining our weather and climate, supports plant growth and makes life possible.

• Evaporation: most water evaporates from the oceans, where water is found in highest
  abundance. However some evaporation also occurs from lakes, rivers, streams and
  following rain.


• Transpiration: is the water loss from the surface area (particularly the stomata) of plants.
  Transpiration accounts for a massive 50


• Evapotranspiration: the processes of evaporation and transpiration are often collec-
  tively referred to as evapotranspiration.


• Condensation: the process by which water vapour is converted back into liquid is
  called condensation. You may have observed a similar process occurring when dew
  drops form on a blade of grass or on cold glass. Water in the atmosphere condenses to
  form clouds.

Chapter 9. Biospheres to ecosystems 281