© 2011 Pearson Education, Inc. Marine Ecosystems Marine ecosystems Why the Ocean Matters.
Energy Flow in Marine Ecosystems
Transcript of Energy Flow in Marine Ecosystems
Energy Flow in Marine Ecosystems
Pg. 23
What are primary producers?
• Organisms need energy for growth, reproduction, & metabolic processes.• No organism can create energy, so obtain it from other sources
• Autotrophs (aka Primary Producers)• Plants, algae & some bacteria • get energy from sunlight or chemicals; convert into forms living cells
can use
• Primary producers• Essential to flow of energy through biosphere• store energy in forms convenient for organisms that eat
them • Example: algae get energy from sunlight, turn it into
nutrients that can be eaten & used for energy by animals such as a copepod
• Photosynthesis (6H2O + 6CO2 � C6H12O6 + 6O2)• Process used by most producers to obtain energy• Algae = main photosynthesizers freshwater & upper ocean • Photosynthetic bacteria (cyanobacteria) = important primary
producers in tidal flats & salt marshes.
How do organisms obtain energy in aphotic ecosystems?
• Biologists discovered ecosystems around volcanic vents in total darkness on the deep ocean floor
• Ecosystems are called “Hydrothermal vents”
• Deep-sea ecosystems depend on chemosynthetic primary producers
• Chemosynthesis - use of chemical energy to produce carbohydrates
• harness chemical energy from inorganic molecules (hydrogen sulfide)
How Do Consumers Obtain Energy & Nutrients?
• Heterotrophs (aka consumers) - Organisms that must acquire energy
from other organisms by ingesting it; classified by energy acquisition
• Herbivores - obtain energy & nutrients by eating plant leaves, roots, seeds, or fruits.
• Ex. Sea urchins, mussels, zooplankton
• Carnivores - kill & eat other animals
• Ex. Tuna, Sea snake, Octopus
• Omnivores - animals that eat a variety of different foods; i.e. plants & animals
• Ex. Blue crabs, sea otter
• Scavengers - animals that consume carcasses of other animals that were killed by
predators or died of other causes.
• Ex. hagfish
• Decomposers - feed by chemically breaking down organic matter.
• decay caused by decomposers is part of the process to produce detritus—small pieces of
dead & decaying plant & animal remains
• Ex. Bacteria
• Detritivores - feed on detritus particles; chew or grind them into smaller pieces;
routinely digest decomposers that live on, and in, detritus particles
• Ex. Sea cucumbers
How does energy flow through ecosystems?
• Energy flows through ecosystems in one-way stream• Energy source � primary producers � consumers
• Food chain: series of steps where organisms transfer energy by eating & being eaten
• Vary in length depending on ecosystem & organisms present
• Ex. Aquatic food chains:
• Primary producers = mixture of floating algae called phytoplankton & attached algae
• Primary consumers = small fishes that eat producers (ex. Flagfish)
• Secondary consumers = large fish (ex. largemouth bass) eat small fish
• Tertiary consumers = birds (ex. Anhinga) eat large fish
• Quaternary consumers = top predator (ex. Alligators) eat birds
• 4 steps in this chain, so top predator/carnivore is four steps removed from primary producer
Example from Everglades (aquatic food chain)
• Feeding relationships are more complicated than single, simple chain
• Many animals eat more than one kind of food (generalists)
• Food Web - network of feeding interactions within ecosystem
• Each path through a food web is a food chain
• A food web links all of the food chains in an ecosystem together
• Detritus pathway: • Most producers die without being eaten.
• decomposers convert dead material to detritus
• eaten by detritivores, such as crayfish, grass shrimp, & worms.
• Pig frogs, killifish, & other fishes eat the detritivores
• Decomposition process releases nutrients to be used by primary producers
• Without decomposers, nutrients would remain locked in dead organisms.
How does energy flow through
ecosystems?
What happens when Food Webs are disturbed?
• When disturbances to food webs happen, the effects can be dramatic.
• Example:
• All animals in Arctic food web depend directly or indirectly on shrimplike animals called krill.
• Recently, krill populations have dropped
• Given structure of food web, a drop in the krill population causes drops in populations of all other members