You now know that animals can be divided into two different categories: those with backbones and those without backbones.
Like animals, plants also have a classification system.
All cells need water, and plants are divided into two groups based on how they deliver water to their cells. These two types are vascular plants and nonvascular plants .
Vascular plants have an organized system to move water and food to their cells. They use roots to absorb water and a tissue called xylem ( zy-lum ) to move it upward to the shoots. Another plant part called phloem (floe-em) moves sugars and other helpful molecules to the plant’s cells. Think of xylem and phloem as a vast highway system, trucking important chemicals throughout the plant. Most land plants are vascular plants, including trees, flowers, shrubs, and the plants that produce fruit and vegetables.
All plants are not created equal!
Some plants do not have a “superhighway” to transport water and nutrients. These kinds of plants are called nonvascular plants. These feathery, spongy plants are some of the most ancient types of plants and first sprouted about 460 million years ago.
Examples of nonvascular plants are mosses, liverworts, and hornworts. Because they cannot easily move water, nonvascular plants need to live in damp areas and grow low to the ground, usually no more than a few centimeters. They don’t have true roots, stems, or leaves. Instead of producing seeds like their vascular cousins, nonvascular plants use spores to reproduce.
Celery is a great plant for observing a vascular system in action. Materials: a stalk of fresh celery
• a glass of water • red food coloring • plastic

knife • stir stick.
1. Carefully cut the white end off the celery. You should be able to see the vascular bundles of xylem and phloem in the celery.
2. Add 2 drops of food coloring to the water. Stir.
3. Put the end of the celery in the glass of water.
Wait a few hours (or even overnight).
4. Take the celery out of the water. What do you observe? The celery should be streaked with color because the vascular system of the plant lets water move easily through it. Cut the celery apart where the streaks are, to see even more detail
Think about the number of different species in the world: Over
300,000 different types of plants, about 50,000 different vertebrates, and a staggering 1,300,000 (and still counting) invertebrates.
Classification systems help organize organisms in order to better understand their similarities and differences.

Food, water, protection from harm —every organism needs these things to live.
You think you’ve got it tough? Try being a ruby-throated hummingbird.
You’d have to collect and eat more than your own weight each day. You would have to fly hundreds of miles through heavy winds and storms to escape bone-chilling cold as you follow the warm weather that will bring you food. And don’t forget there are plenty of other animals who would just love to turn you into a bite-sized snack. Surviving is hard work!
In order to survive, all organisms need these things: water, an energy source (food), and protection from harsh weather and other organisms.
If all members of a particular species fail to survive, it is called extinction.
Some scientists estimate that 99% of all species that ever lived are now extinct, almost all by natural causes. Unfortunately, human pollution and habitat destruction have recently caused many species to become extinct and many more species are now threatened.
One example is the Chinese river dolphin. It has not been seen since 2002 and is now believed to be extinct.
Overfishing, pollution, and human development share the blame.
All animals must eat to survive, and they have many different ways to get their food.
Carnivores (animals that eat other animals) tend to be stealthy, patient hunters. Some carnivores such as polar bears, wolves, and owls rely on powerful muscles and sharp teeth or claws to catch their prey. Orcas, hyenas, and lions use teamwork when hunting for food, increasing their chances for a decent meal.
Many animals are omnivores (eating both animals and plants) or herbivores (eating only plants). And speaking of plants —why don’t we eat hay? Cows, koalas, and horses can digest hay because of unicellular organisms that live in their stomachs. These tiny organisms also must eat to survive, so they digest hay. We humans do not have these tiny bacteria in our stomachs so hay is inedible to us.
Some animals have a special behavioral adaptation for surviving during times with little

food. Most bears find it difficult to find enough fish, nuts, and berries in the winter, so they hibernate during the coldest months when their food supplies are low. Other animals, such as chipmunks, squirrels, skunks, and bats are cold-weather snoozers too.
Plants have a different set of adaptations that allow them to survive. Some produce poisons to prevent them from becoming a meal for a hungry animal. Others grow thorns or thick bark to shield them from attack. All plants need water. Some plants —called deciduous ( dih-sid-you-us ) plants —become dormant , shedding their leaves in winter to conserve water and save energy. Plants also compete for sunlight. Trees are the masters of growing tall to capture more sunlight than the smaller plants beneath them.
All plants also need nutrients, which they normally absorb through the soil. Some plants, such as the Venus flytrap and the pitcher plant, grow in places with nutrient poor soil, so they have evolved the ability to digest insects to get the nutrients they need. These plants still make their own food by harvesting the element carbon from the air through photosynthesis. Think of the insects that they “eat” as being a bit like vitamins for the plant.
It’s a tough world out there. Part of being an animal is the fact that some other animal is hoping to turn you into its lunch. To survive, animals have evolved many different ways to defend themselves against predators. Some animals camouflage themselves so they can’t easily be spotted. For example, the snowshoe hare grows brown fur during the summer and white fur during winter to blend in with its surroundings.
Would you eat a sandwich that smelled terrible? Probably not. Animals such as skunks and some insects make stinky smells that repulse would-be attackers. Turtles, rhinos, and sea urchins grow their own natural armor for protection.
Another adaptation is called mimicry , when one animal behaves, sounds, smells, or looks like another animal. For example, the false cobra is a fairly harmless snake that looks so much like the poisonous cobra that other animals tend to leave it alone. Finally, animals can use speed and their own senses
(such as keen hearing and smell) to avoid getting caught.
Getting food and water isn’t always easy. The Namibian web-footed gecko
(below) lives in a dry desert. It gets water by letting early-morning mist collect on its eyeballs, and then licking it off!
Leaf-cutter ants are considered the first farmers. These insects cut

down leaves, put them in a
“garden,”and then their ant babies eat the fungus that grows on the leaves!