Created by Alejandro Gutierrez and Alejandro Garza A brief presentation of the topics 3.3 and 3.4 from the Biology book from Pearson.

1. Topics 3.3 and 3.4
By: Alejandro Gutiérrez
& Alejandro Garza

2. Food chain
 The energy passes through an ecosystem along a food chain
 Food chain: Series of steps in which organisms transfer energy by
eating and being eaten. They vary in length.

3. Food web
 In most ecosystems, feeding relationships are
much more complicated than the relationships
described in a single, simple chain.
 A food web is a complex network of feeding
interactions.

4. Food web

5. Disturbance in food webs
 The balance of a food web is very delicate, and any
disturbance may ocassion a change in it.
 For example, in case of oil spill, it would affect the
number of bacteria and fungi, and these are the ones
that break down detritus, ocassionating further
changes.

6. Trophic leves and ecological
pyramids
 Trophic level: Each step in a food web.
 Ecological pyramid: Shows the relative amount of
energy or matter contained within each trophic level in
a given food chain or food web. There are 3 types:
Pyramids of energy, pyramids of biomass, and
pyramids of numbers.

7. Pyramids of energy
 Show the relativa amount of energy available at each
trophic level of a food chain or web.

8. Pyramids of Biomass
 Biomass: Total amount of living tissue within a given
trophic level.
 Illustrates the relative amount of living organic matter
available at ech trophic level in an ecosystem.

9. Pyramid of numbers
 Shows the relative number of individual organisms at
each trophic level in an ecosystem.

10. Biogeochemical cycles
 Unlike the one-way flow of energy, matter is recycled
within and between ecosystems. Elements pass from
one organism to another and among parts of the
biosphere through closed loops (biogeochemical cycles),
powered by the flow of energy.

11. Water cycle

12. Carbon cycle

13. Nitrogen Cycle

14. Phosphorus Cycle