Question

Photosynthetic autotrophs receive energy from
A. Inorganic chemical
B. Organic chemicals
C. Heat
D. Light

Answer 1

Hint: Autotroph, refers to the organism that acts as primary producers in a food chain. They obtain energy and nutrients by using sunlight through the process of photosynthesis or chemical energy through oxidation to make organic substances from inorganic ones. They do not consume other organisms but are consumed by heterotrophs.

Complete answer:
Autotrophs are extremely important as all life forms are dependent on them. Without plants that create sugars from carbon dioxide gas and sunlight via the process of photosynthesis, for example, no herbivorous animals could exist, and no carnivorous animals that eat herbivores could exist.
Types of Autotrophs:
They are classified on the mode of obtaining energy into- photoautotrophs, and chemoautotrophs.
Photoautotrophs:
These organisms obtain energy to make organic materials from sunlight. Plants, green algaes, and bacteria which perform photosynthesis come under this type. Photoautotrophs capture photons from the Sun and harvest their energy, using it to perform important biochemical processes such as making ATP. Many photoautotrophs take carbon from the atmosphere and use it to make sugars and other molecules that store the Sun’s energy in their molecular bonds.
Chemoautotrophs
Chemoautotrophs are organisms that obtain energy from inorganic chemical processes. They use volatile chemicals such as molecular hydrogen, hydrogen sulfide, ferrous iron, and ammonia as their energy sources which further help them to survive in places that would be toxic to many other organisms, as well as places without sunlight. Chemoautotrophs are usually bacteria or archaebacteria.
Examples of Autotrophs
Plants
Plants (except Venus fly traps which can eat insects) are photoautotrophs. They produce sugars and other essential ingredients by using their pigments, such as chlorophyll, to capture photons and harness their energy. When plants are consumed by animals, animals use that energy and organic materials for themselves.

Therefore, the correct answer is D, light.

Note: It is thought that free oxygen was not present in Earth’s atmosphere until after photoautotrophs became common in Earth’s seas. A large amount of free oxygen reacted with iron that had previously been dissolved in ocean water and turned into rust. This process created rocks called banded iron formations. Release of large amounts of free oxygen into Earth’s atmosphere by photoautotrophs paved the way for the survival of large animals (including humans) that need the highly efficient process of aerobic respiration.