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Course: Middle school biology - NGSS > Unit 5
Lesson 2: Matter and energy in foodwebsWorked example: analyzing an ocean food web
We can analyze the arrows in a food web to identify producers, primary consumers, secondary consumers, and decomposers. Created by Khan Academy.
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- One thing. What about the kelp that grows deeper in the ocean? How do they get their energy? Cause there is very little if no sunlight.(8 votes)
- Although kelps resemble land plants, they are uniquely adapted to life in cool, clear, moving water. They depend on moving water to provide a steady supply of nutrients for photosynthesis. As water flows by the blades, their serrated edges help to increase water mixing.(4 votes)
- what do you call some thing that eats secondary consumers(0 votes)
- Tertiary consumers, they eat primary and secondary consumers.(13 votes)
- wouldn't the bacteria technically be a secondary consumer also because it's eating the fish.(1 vote)
- No. It is not preying upon anything — actually, it is just feeding upon the creatures once they have already died, thus making it a decomposer!
So, in reality, bacteria are not consumers at all!
Hope this helps!(9 votes)
- What would you call something that eats the secondary consumers?(3 votes)
- Tertiary consumers are animals that eat secondary consumers. For example, a slug(a primary consumer) eats a leaf(producer). A little bird, say a robin(secondary consumer) comes and eats the slug. Then, a hawk(he tertiary consumer) will eat the little robin.
(Not AI generated)
Hope this helps!(4 votes)
- One thing. What about the kelp that grows deeper in the ocean? How do they get their energy? Cause there is very little if no sunlight.(3 votes)
- That’s a great question!
Kelp, like other plants, typically relies on photosynthesis to produce energy, a process that requires sunlight. However, in deeper parts of the ocean where sunlight is scarce or non-existent, kelp and other marine plants have adapted to survive in these conditions.
Some species of kelp have developed the ability to absorb and utilize the blue-green light that penetrates deeper into the water. They have special pigments in their cells that can capture and use this light for photosynthesis.
In areas where light is completely absent, life still finds a way. Some organisms rely on chemosynthesis, a process that uses chemical reactions to create energy. Instead of using light as a source of energy like photosynthesis, chemosynthetic organisms use chemicals like hydrogen sulfide or methane. This is common in extreme environments like hydrothermal vents on the ocean floor.
So, while kelp generally relies on photosynthesis and the availability of sunlight, life in the deep oceans has found other ways to produce energy.(3 votes)
- Why isn't the otter a primary consumer?(2 votes)
- because it doesn't eat producers.(5 votes)
- How do underwater plants get sunlight? How does kelp do photsynthesis?(1 vote)
- Underwater plants are no different from their surface relatives. They still harness the suns energy to produce glucose to be stored in their systems.
This is why you normally see life thriving in shallower parts of the ocean (Closer to the sun) rather than in the deeper sections of the sea. (Twilight or Midnight Sectors)
Hope this helps!(5 votes)
- some decomposers can be eaten (mushrooms) but does anything eat bacteria (not on accedent)(3 votes)
- Can't for example the urchin or kelp die and get eaten by decomposers?(2 votes)
- In some of the animals, in their name was plankton, what does plankton mean?(2 votes)
Video transcript
- [Instructor] So this
diagram right over here describes a food web. And a food web models how energy and matter
moves in an ecosystem. And we're going to use this food web to answer some questions, to make sure we understand food webs. So the first thing I'm
going to ask you is, what are the producers in this food web. Pause this video and see
if you can figure this out. All right, now let's work
through this together. The producers are the ones that can take matter in the
ecosystem, in the environment, and energy from an outside
source, usually the sun, in order to construct themselves and also in order to store that energy. And when you look at a food web, producers are going to have
arrows pointed away from them. So they're getting their energy and their matter from the environment and then other people are
going to consume them. And we're gonna talk about
them in a little bit. But we can see here that
the kelp is a producer. This is an aquatic ecosystem
that we're looking at. But the kelp is a producer. There's no arrows going into it so it's using the sun and
elements and atoms and molecules that it's finding in its
environment in order to grow. And we can also see that's the
case with the phytoplankton. It's also able to do
photosynthesis, like the kelp, and capture that energy from the sun. Now, the next question I have
is, where are the decomposers? Pause the video and
try to answer that one. All right. Now you might remember decomposers, you can think about that's where a lot of the energy and the matter ends up, to be decomposed and then recycled again and be reused again by the producers. And if you're looking at a food web, these would-be organisms where all of the arrows point to them, but you don't have any
arrows coming from them. And over here, it's
clear that the bacteria, and there's many different
species of bacteria or many different types of bacteria, but the bacteria here are the decomposers. Next, I am going to ask you about the primary consumers. Pause this video and see
if you can identify them. Well, primary consumers are consumers that directly eat the producers. And so let's see, who is eating the kelp? You have have the sea
urchin eating the kelp. You have the fish eating the kelp. Who's eating the phytoplankton? You have the zooplankton
eating the phytoplankton. So these are primary consumers. Next, let's think about
secondary consumers. Secondary. These are those that
eat primary consumers. Pause the video and think about that. Well, let's think about who's eating these primary consumers. You have the otter. What's interesting is the
fish is a primary consumer because it consumes kelp,
which is a producer, but it also can consume
another primary consumer. So, a fish, or the fish here, are both primary and secondary consumers. And then I think we are done. So you can see the general notions here. The producers have arrows
going away from them but no arrows coming into them because they're getting
their energy from the sun and they're using the
matter in the ecosystem. Primary consumers are
eating those producers, and you can see they have
arrows going into them. And then they're eaten by other
folks, secondary consumers, or those that eat the primary consumers. And then last but not least,
you have the bacteria, which are decomposers, where
the arrows all point to them and they continue to use that energy and then they take those
nutrients, those molecules, and they put 'em back into the ecosystem so that it can be recycled again.