Animals have specialized features that plants generally lack: they take in food rather than making sugars through photosynthesis, and most can move their bodies and sense their surroundings using nervous systems. The clearest biological distinction, however, is not movement or eating; it is how their cells are organized and how they obtain energy and nutrients.
The Basic Difference Between Animals and Plants
Animals and plants are both eukaryotes, meaning their cells contain a nucleus and other internal compartments. They are also both multicellular in the familiar examples people encounter, and both need energy, water, and materials to grow. But they meet those needs in different ways. Plants generally make energy-rich sugars from carbon dioxide and water using light, while animals obtain organic nutrients by consuming other organisms or their products.
That contrast is a useful starting point, not a complete definition. Some plants are parasitic or otherwise rely partly on nutrients from other organisms, and animals can have partnerships with photosynthetic microbes. A feature shared by many animals and plants, or missing in a few unusual cases, does not by itself settle which kingdom an organism belongs to. Biologists classify organisms using a combination of cellular structure, development, nutrition, and evolutionary relationships.
Cell Walls, Chloroplasts, and Cell Shape
A typical plant cell has a cellulose cell wall outside its cell membrane. The wall helps support the cell and resist pressure as water enters. Many plant cells also contain chloroplasts, the structures where photosynthesis takes place. A large central vacuole, which stores water and dissolved substances, is another common feature of plant cells.
Animal cells generally lack cellulose walls and chloroplasts. Without a rigid wall around each cell, animal tissues can form flexible shapes and change their arrangements. Cells can move relative to one another, which is useful in muscles, blood, and developing embryos. Animals still have internal structural support: proteins inside cells help maintain shape, and many animals also have skeletons or other supporting tissues. Those supports are not equivalent to the cellulose walls surrounding plant cells.
These are general distinctions, not a rule that every cell in every plant or animal looks the same. For example, some plant cells lose their chloroplasts as they mature, while green plant tissues contain many chloroplasts. A plant root cell typically does not photosynthesize, even though it belongs to a photosynthetic organism.
How Animals Get Their Food
Most animals are heterotrophs: they obtain carbon and nutrients from organic material made by other organisms. Many take in food through a mouth or other opening, break it down through digestion, and absorb usable molecules. A grazing mammal, a filter-feeding shellfish, and a spider that consumes prey use very different methods, but all rely on food produced by other organisms.
Plants are usually described as photosynthetic producers. In photosynthesis, light energy helps convert carbon dioxide and water into sugars, releasing oxygen as a by-product. Plants also take up mineral nutrients, such as nitrogen and phosphorus, from their surroundings. Photosynthesis does not mean that plants need no food-related inputs: they need raw materials and energy, and they use sugars to build and power their tissues. The key difference is that plants typically make much of their organic food, whereas animals acquire it from outside.
There are exceptions worth knowing. Some plants trap insects, but they do so mainly to obtain mineral nutrients in nutrient-poor environments; they still photosynthesize. Conversely, some animals host algae or other photosynthetic partners. Those partnerships can supply some resources, but the animal remains an animal because classification reflects its biology and evolutionary history, not one unusual source of nourishment.
Movement: A Common Trait, Not a Perfect Test
Animals are usually capable of moving from place to place during at least one stage of life. Muscles, flexible tissues, and coordinated body systems make this possible in many species. A fish swims, an insect flies, and a worm crawls. Some animals are attached to a surface as adults, however. Sponges and many shellfish, for instance, may spend much of adult life fixed in place, even though their bodies or life cycles show other forms of movement.
Plants usually remain rooted or anchored, but they are not simply motionless. Shoots can grow toward light, roots can grow in response to gravity, and leaves or flowers may open and close. These movements arise largely from growth or changes in cell pressure rather than the rapid, coordinated muscle action typical of animals. The distinction is therefore between kinds of movement, not movement versus no movement.
Senses, Nerves, and Fast Responses
Most animals have sensory cells that detect features such as light, chemicals, touch, temperature, or sound. In many animal groups, neurons carry signals, and nervous systems coordinate responses. This arrangement can support rapid behavior: an animal may turn toward food, withdraw from harm, or change course while moving. The form and complexity of these systems vary greatly; not every animal has a brain, and simple animals can respond without one.
Plants also detect and respond to their environment. They sense light direction, gravity, water availability, and other conditions, and they adjust growth or internal activity accordingly. They do not have neurons or brains, but that does not mean they are unaware in the everyday sense of detecting conditions. Their signaling relies on different cellular and chemical processes, often unfolding more slowly than an animal’s immediate movement.
A common misconception is that plants must have animal-like feelings or thoughts because they respond to stimuli. A response alone does not demonstrate a nervous system or conscious experience. Scientists distinguish observable signaling and growth from claims about subjective experience, which cannot be inferred merely from a plant bending toward light.
How Their Bodies Grow and Develop
Many animals have a relatively fixed body plan after development. They grow, but their basic arrangement of organs and body parts often remains recognizable. Many plants, by contrast, keep producing new leaves, roots, and stems from growing regions throughout life. This growth pattern helps a plant adjust its form as conditions change and lets it expand toward resources.
Animal development often involves cells moving to new positions and forming tissues and organs in coordinated sequences. Plant development also involves carefully regulated growth, but a rigid cell wall limits how plant cells move past one another. Plants commonly shape organs by controlling where cells divide and how they enlarge. These differences help explain why animal bodies can form mobile limbs and plant bodies can keep adding branches or roots.
Reproduction and Life Cycles
Both plants and animals reproduce sexually, and many also have forms of asexual reproduction. Their life cycles differ in important ways. Animals commonly produce eggs and sperm, which join during fertilization to begin development. Plants can also make eggs and sperm, but their reproductive cycles often include structures and stages that have no close equivalent in familiar animals. Flowering plants, for example, use pollen to deliver sperm cells to an egg-bearing structure.
Some animals reproduce by budding, fragmentation, or other asexual methods. Plants can reproduce through seeds, spores, runners, bulbs, or pieces that grow into new individuals, depending on the group. These are broad patterns rather than universal rules. Reproduction alone is not a reliable way to tell whether an unfamiliar organism is an animal or a plant; its full life cycle and cellular biology matter.
Animals and Plants Compared
The comparison below describes common patterns. It should not be treated as a checklist in which one unusual trait determines an organism’s identity.
- Nutrition: Animals generally consume organic material; plants usually make sugars through photosynthesis.
- Cell walls: Typical animal cells lack cellulose walls; plant cells usually have them.
- Chloroplasts: Animals do not have chloroplasts as part of their own cells; photosynthetic plant tissues commonly do.
- Coordination: Many animals use neurons and, sometimes, a brain; plants coordinate responses without nervous systems.
- Movement: Many animals move their bodies through muscular action; plant movement is often growth-based or driven by changes in cell pressure.
- Growth: Many plants continue making new organs from growing regions; many animals settle into a more fixed body plan as they mature.
Common Misconceptions
“Animals move, and plants do not.” This misses both sides of the comparison. Some adult animals stay attached, while plants move through growth and changes in their tissues. Movement is useful evidence, but it is not the defining boundary.
“Anything that eats is an animal.” Insects caught by a carnivorous plant do not turn the plant into an animal. The plant uses prey mainly as a source of minerals and continues to make sugars through photosynthesis.
“Plants are simple because they have no brain.” Plants lack animal nervous systems, but they regulate growth, transport materials, and respond to complex environmental conditions. Different body plans solve biological problems in different ways; a brain is not a universal measure of complexity.
“Every living thing is either a plant or an animal.” Many organisms belong to neither group. Fungi, bacteria, and numerous single-celled eukaryotes have their own classifications. Mushrooms, for example, are not plants: fungi absorb nutrients from their surroundings rather than making food by photosynthesis.
Frequently Asked Questions
What is the main thing animals have that plants do not?
The strongest simple answer is that animals typically have cells without cellulose walls and obtain food by consuming organic material. Many also have muscles and nervous systems, but those traits are not present in every animal and are not the whole definition.
Do all animals have brains?
No. Many animals have brains, but some have simpler nervous systems, and some lack a centralized brain. An animal is not defined by having a brain; its classification depends on a wider set of biological and evolutionary traits.
Can plants move?
Yes. Plants can change position or shape through growth, and some plant parts move as cells change pressure. These movements generally differ from an animal moving its body with muscles, but plants are not entirely motionless.
Are carnivorous plants animals because they catch insects?
No. They remain plants. Catching prey helps them obtain certain nutrients, while photosynthesis supplies sugars. Their feeding adaptation does not change their basic cellular organization or evolutionary group.
Are fungi plants or animals?
Fungi are neither. They are a separate group of eukaryotes. Like animals, fungi obtain nutrients from organic material, but their cells commonly have walls made from different materials than plant cellulose walls, and they have their own distinctive biology.
The Short Answer
Animals generally consume food, lack the cellulose cell walls and chloroplasts typical of plant cells, and often use muscles and nervous systems to move and respond. Plants typically make sugars through photosynthesis, have cell walls, and respond through growth and other cellular processes. These contrasts explain the everyday difference, while exceptions and other living groups show why classification relies on several traits rather than a single test.