Main content
Middle school biology - NGSS
Course: Middle school biology - NGSS > Unit 5
Lesson 1: Photosynthesis in ecosystemsPhotosynthesis in ecosystems
Oxygen produced by photosynthesis is released and used by animals and plants in respiration. Animals depend (directly or indirectly) on food from photosynthetic organisms for growth and survival. Created by Khan Academy.
Want to join the conversation?
How do plants get energy?(2 votes)
Plants obtain their energy through the chemical process known as photosynthesis which converts the sun's energy into energy useful for living organisms. Photosynthesis is represented by this chemical equation.
6CO2 + 6H2O → C6H12O6 + 6O2
This means that plants take six carbon dioxide molecules, (the 6CO2) and six water molecules (6H2O), and, with the addition of the sun's energy and the catalyst chlorophyll, can create one molecule of glucose (C6H12O6) and six molecules of oxygen (O2).
The energy is contained in the glucose molecule produced by the reaction. When the cell needs to use this energy, it goes through a process known as cellular respiration which (in summary) breaks down the molecule and releases the energy stored inside.
Animals cannot perform photosynthesis (clearly), so that is the reason that we need to eat. When plants are eaten, the glucose (and thus the energy stored within) is transferred into our system where we can use it. Even eating animals gives use the energy initially held in plants as it transfers up the food chain. If animals could perform photosynthesis, there would be no need to consume anything. So plants harvest and convert the sun's energy into a form that any organism can take advantage of.
(On a side note, plants are not the only organisms that perform photosynthesis. Algae and some types of bacteria known as cyanobacteria perform it as well.)
KA has a whole unit in their Biology Library about this. You should check it out.
https://www.khanacademy.org/science/biology/photosynthesis-in-plants(21 votes)
"Now, animals like you and me,"(8 votes)
because you need it to live(0 votes)
I don't understand what he meant by "we can do this in reverse" can someone explain it to me?(0 votes)
Photosynthesis uses energy (from sunlight) to combine carbon dioxide and water to make sugar and oxygen.
Cellular respiration reverses this reaction. It releases energy by mixing oxygen and sugar to make carbon dioxide and water. We use this energy that cellular respiration releases to live.
Does that help at all?(12 votes)
Why do we need oxygen(0 votes)
Oxygens primary function is to provide our body with energy.
Our lung oxygenate the blood that blood goes through the left atrium then to the left ventricle from the left ventricle to the Aorta. From there it will go to the upper or the lower body where the oxygen is off loaded to the tissues then as a byproduct deoxidated blood will be pumpt back.(Your cells, in the little organelles called mitochondria which are energy generators: they use oxygen to transform nutriments from the digestive process into energy that can be used directly by the cell). The deoxygenated blood will go through your superior and inferior vena cava to your right atrium there it will go to your right ventricle to your left and right pulmonary artery back to your lungs where it will be filtered and go back into the air.(7 votes)
yellow squiggles coming from the sun XD(2 votes)- The drawing hack we used in kindergarten xD(3 votes)
- Did he just call us a animal?(3 votes)
Yep, we are animals, we are all multicellular organisms.(0 votes)
Plants breathe CO2 and exhale oxygen while humans breathe oxygen and exhale CO2,
So it's kind of a symbiotic relationship(2 votes)- Why is Khanmigo telling me that it has a limited amount of "AI power"? What is "AI power"?(2 votes)
- Ararat intelligent(1 vote)
plants get energy from the sun(1 vote)- Yes, plants get energy from the sun through Photosynthesis.(2 votes)
Video transcript
- [Instructor] When you look at a rainforest ecosystem like this, one of the obvious questions may be, where do these plants come from? How do they grow? They're growing all the time, they're getting larger
and larger and larger. Where does that mass, where
does that matter come from? Pause this video and think about that. Well, you might already be
guessing where it comes from. It might have something
to do with photosynthesis, which we go into a lot
of depth in other videos, but this is a process where
you have carbon dioxide from the air in conjunction with water that primarily is coming from the soil, and it uses energy from the sun so I'll just draw that in, these yellow squiggles
coming from the sun, in order to do two things. The plant is going to be building itself using the matter in the
carbon dioxide and the water while also expelling
oxygen as a byproduct. And this matter that the plant is able to take from its environment
with photosynthesis is used to both become
the structure of the plant and a store of energy
in the form of sugars. Now, animals like you and me, we get our energy by
then eating these plants. And how do we unlock that energy? Well, that's where this
oxygen is really useful. That's why we need to breathe oxygen because by breathing the oxygen, we can essentially do
photosynthesis in reverse, and we can break down this matter, these sugars, that we're
getting from plants. So all of this biomass is coming from essentially water from the soil and carbon dioxide,
and energy from the sun is used essentially put it together. There might be a few other nutrients that are also coming from the
environment, like the soil, but primarily the water
and the carbon dioxide.