Why do photosynthesis occur

To fulfill this basic need, all living things either make their own food or get it from some other source. Humans can eat both plants and animals. Some animals consume other animals, while some animals eat plants as their food.

Ultimately, we see that everybody on this planet is dependent on plants for their food. But then, what do plants eat? The process by which land plants produce their own food using sunlight and carbon dioxide is known as photosynthesis Figure 1. While carbon dioxide is absorbed by the leaves, the sunlight is captured by a chemical molecule in the plant, called chlorophyll Chl. All photosynthetic organisms contain Chl. Plants in the oceans face problems with light availability.

The blue and green portions of light penetrate into the water more than the yellow and red portions of light do Figure 2. Luckily, ocean plants get help in producing food from such limited light and carbon dioxide, from tiny microscopic microbes called cyanobacteria also known as blue-green algae. These microbes have adapted to dim light conditions, and they carry out photosynthesis both for themselves and for the benefit of other living things.

Cyanobacteria are ancient microbes that have been living on our earth for billions of years. Cyanobacteria are said to be responsible for creating the oxygen-filled atmosphere we live in [ 1 ].

For carrying out photosynthesis in low light conditions, cyanobacteria have the help of proteins called phycobiliproteins , which are found buried in the cell membranes the outer covering of the cyanobacteria.

Phycobiliproteins play the role of assistants to Chl in aquatic water environments. Since light has a difficult time penetrating into the oceans, phycobiliproteins make this job easier by absorbing whatever light is available; they absorb the green portion of the light and turn it to red light, which is the color of light required by Chl [ 2 ]. A Coleochaete orbicularis Charophyceae gametophyte; magnification x 75 photograph courtesy of L. B Chara Charophyceae gametophyte; magnification x 1.

C Riccia liverwort gametophyte showing sporangia black embedded in the thallus; magnification x 5 photograph courtesy of A. D Anthoceros hornwort gametophyte showing unbranched sporophytes; magnification x 2. E Mnium moss gametophyte showing unbranched sporophytes with terminal sporangia capsule ; magnification x 4. F Huperzia clubmoss sporophyte with leaves showing sessile yellow sporangia; magnification x 0.

G Dicranopteris fern sporophyte showing leaves with circinate vernation; magnification x 0. H Psilotum whisk fern sporophyte with reduced leaves and spherical synangia three fused sporangia ; magnification x 0.

I Equisetum horsetail sporophyte with whorled branches, reduced leaves, and a terminal cone; magnification x 0. J Cycas seed plant sporophyte showing leaves and terminal cone with seeds; magnification x 0. Origin of land plants. New York: J. Wiley and Sons, All rights reserved. Part B: courtesy of M. Feist, University of Montpellier.

Coleochaete orbicularis. Both the gametophyte and the background are bright green. The gametophyte has an irregular circular shape and a scalloped edge. It is divided into many box-like segments cells , each with a visible, round nucleus inside. Panel b shows a Chara gametophyte.

The organism has branching, tendril-like leaves reaching from a primary stalk. The green leaves are punctuated with small, round, yellow structures. A green liverwort gametophyte, In panel c, is protruding from the soil. Its four primary stems each diverge into two halves and then branch again at their termini, so that each has a forked end. Panel d shows a hornwort gametophyte.

Each green stem resembles a single blade of grass. Panel e shows moss gametophytes with sporophytes protruding from the ground. The gametophytes have small green leaves, and the sporophytes are thin, unbranched, brown stalks. Each sporophyte has a fluorescent orange, oviform capsule called a sporangia perched on top of its stalk. Panel f shows six clubmoss sporophytes emanating from the ground.

Some stand vertically out of the soil, and some curve or have fallen horizontally. They have many stiff, protruding, spine-like, green leaves. The sporangia are small yellow balls at the base of the leaves. Panel g shows fern sporophytes with many stems covered with small, elongated, symmetrical green leaves. Panel h shows a whisk fern sporophyte with long, straight, green stems beaded with yellow, round synangia along their lengths. In panel i, a horsetail sporophyte is shown.

It has a single long stem, which is surrounded by a skirt of green leaves at its base and an elongated, yellow cone at the top. Here is the word equation for photosynthesis:. Photosynthesis takes place inside plant cells in small objects called chloroplasts. Chloroplasts contain a green substance called chlorophyll. This absorbs the light energy needed to make photosynthesis happen. Plants and algae can only carry out photosynthesis in the light. You cannot download interactives. Plants are autotrophs, which means they produce their own food.

They use the process of photosynthesis to transform water, sunlight, and carbon dioxide into oxygen, and simple sugars that the plant uses as fuel. These primary producers form the base of an ecosystem and fuel the next trophic levels. Without this process, life on Earth as we know it would not be possible. We depend on plants for oxygen production and food. Learn more about this vital process with these classroom resources.

Chlorophyll is a pigment that gives plants their green color, and it helps plants create their own food through photosynthesis. What does a plant leaf have to do with the solar energy panels on the White House? Producers convert water, carbon dioxide, minerals, and sunlight into the organic molecules that are the foundation of all life on Earth.

Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Green Tree Leaves The plant leaves are green because that color is the part of sunlight reflected by a pigment in the leaves called chlorophyll. Photograph courtesy of Shutterstock. Twitter Facebook Pinterest Google Classroom.

Encyclopedic Entry Vocabulary. The process During photosynthesis, plants take in carbon dioxide CO 2 and water H 2 O from the air and soil.