Figure 18.4: Coral reefs are complex and beautiful ecosystems. ( 6 )consumers.
There are two types of producers. Nearly all producers take energy from the Sun and make it
intochemicalenergy(food)bytheprocessofphotosynthesis. Photosynthesizingorganisms
use carbon dioxide (CO 2 ) and water (H 2 O) to produce sugar (C 6 H 12 O 6 ) and oxygen (O 2 ).
This food can be used immediately or stored for future use.
A tiny group of producers create usable chemical energy from chemicals, without using any
sunlight. At the bottom of the ocean, at deep-sea hot springs known as hydrothermal vents,
a few types of bacteria break down chemicals to produce food energy. This process is called
chemosynthesis(Figure18.5).
There are many types of consumers. Herbivoreseat producers directly (Figure18.6).
These animals break down the plant structures to get the materials and energy they need.
Many other consumers eat animals. These are known ascarnivores. Carnivores can eat
herbivores or they can eat other carnivores. Omnivoreseat plants and animals, as well as
fungi, bacteria and organisms from the other kingdoms.
There are many types of feeding relationships between organisms. Apredatoris an animal
that kills and eats another animal (Figure18.7). The animal it kills is itsprey.
Scavengersare animals that eat organisms that are already dead. Vultures and hyenas
are just two types of scavengers. Decomposersbreak apart dead organisms or the waste
material of living organisms, returning the nutrients to the ecosystem. Many decomposers
are bacteria, but there are others as well, including fungi (Figure18.8). Decomposers are
recyclers; they make nutrients from dead organisms available for living organisms.