Ch. 1: “Watersheds
and Wetlands”
Lesson 1.3: “Stream
Biology”
Introduction

Streams and rivers are aquatic ecosystems that
are often teeming with life. In addition to
mosses, grasses, ferns, and other plants found
in and along streams and rivers, there are three
dominant groups of organisms in most stream
communities. These include (1) algae and other
protists, (2) invertebrates, and (3) vertebrates.
1. “Stream Biology”
Algae and Other Protists:
 Algae are plantlike protists.
 Algae can make their own food, therefore,
they are known as producers or autotrophs.
 Because they make their own food, algae
form the base of most food chains.
 Animal-like protists include ciliates,
flagellates, and amoebae.
Algae
Food Chain
Finish your food web activity.
Hang it on bulletin board.
Questions: Write out the following questions
and their answers. Hang these with your food
webs.
1. How much energy is passed on from one level
to the next in your ecosystem?
2. Hypothetically remove one organism from your
food web. Hypothesize the effect this will have on
your ecosystem.
3. Add an “invasive species” to your ecosystem.
Hypothesize the effects this will have on your
ecosystem.
Within an ecological food chain, consumers are categorized into
three groups: primary consumers, secondary consumers, and the
tertiary consumers.[2]
Primary consumers are usually herbivores, feeding on plants and
fungus.
Secondary consumers, on the other hand, are mainly Carnivore
and prey other animals. Omnivores, who feed on both plants and
animals, can also be considered a secondary consumer.
Tertiary consumers, sometimes also known as an apex predator,
are usually on top of food chains, capable of feeding on secondary
consumers and primary consumers. Tertiary consumers can be either
fully carnivorous or omnivorous. Humans are one such example of a
tertiary consumer.
Scavenging is both a carnivorous and a herbivorous feeding
behavior in which the scavenger feeds on dead animal and plant
material present in its habitat
Decomposers or saprotrophs are organisms that break down dead
or decaying organisms, and in doing so carry out the natural process
of decomposition
Explain what effect, if any, an
introduced (non-native)
organism will have on the food
web.
1. “Stream Biology”
Invertebrates:
 the most common types of freshwater
invertebrates:
1. insects
2. mollusks
3. worms
 Most of these aquatic invertebrates feed on
algae and plants, and thus they are primary
consumers.
Insects
Mollusks
Worms
1. “Stream Biology”
Vertebrates:
 Examples of amphibians:
1. salamanders
3. newts
2. frogs
4. toads
 Examples of fish:
1. Fish that are primary consumers are called
grazers, strainers, or suckers depending on how
they feed.
2. pike, pickerel, gars, and bullheads examples of
predatory fish.
3. The third group of fish are known as detritivores
(they feed on decomposing plant and animal matter,
including feces)
Salamanders, Frogs, Newts &
Toads
Pike, Pickerel, Gar & Bullhead
Primary Consumers: strainers,
grazers, and suckers.
Detritivores
2. “Factors That Affect
Freshwater Ecosystems”
Define biotic factor: living component of
an ecosystem
 Define abiotic factor: nonliving physical
and chemical parts of an ecosystem

2. “Factors That Affect
Freshwater Ecosystems”

List examples of abiotic factors and
describe/explain the effects each one has on the
stream and on specific organisms living there:
1. stream order
2. temperature
3. current and velocity
4. substrate
5. sunlight
2. “Factors That Affect
Freshwater Ecosystems”

List examples of abiotic factors and describe/explain the
effects each one has on the stream and on specific
organisms living there:
6. turbidity
7. dissolved solids
8. dissolved gases:
oxygen
carbon dioxide
9. organic matter
10. pH