Structures of Life: How are plants and animals suited to live in their environments?

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From where do seeds come and what properties do they have?

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Parts of a Seed

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Seeds and eggs are similar. Both are structures to feed and protect a baby plant or animal. The seed coat, like the egg shell, protects the life inside. The inside of the seed, like the inside of the egg, have food for the embryo (unborn baby).

The growing chick

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The Germinating (Sprouting) Seed

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When plants germinate (sprout), one of the first things we observe are the roots. As the plant grows, the roots' job is to take in water and nutrients (food). Nutrients plants need are phosphorus, nitrogen, and potassium. The leaves take in carbon dioxide (CO2) and sunlight, in order for the plant to produce food.

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Plants usually grow in soil because soil contains those nutrients from decomposed living things, but we can also grow plants in water as long as we add those nutrients. Growing plants in water is called hydroponics. Tomatoes and cucumbers are often grown this way.

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We began studying the crayfish by identify their body structures. The observable parts of an organism (living thing), such as the leaves of a plant or the pincers of the crayfish are called the structures. Crayfish are crustaceans. Crustaceans are a class of mostly aquatic animals that have hard, flexible scales, jointed legs, and two pairs of antennae.

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Crayfish structures and their function:

  • Bristles are the short hairs on the crayfish that help them sense things in their environment.
  • The carapace is the main body shell of crustaceans.
  • The little leg-like parts (structures) are called the swimmerets.
  • Pincers are the claws that help the crayfish kill food and defend themselves.
  • The antennae help them feel around.

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Habitat is the natural environment of a plant or animal. There are more than 500 species of crayfish, and they can survive in environments with fresh water (no salt water). You can find crayfish in lakes, streams, ponds, marshes, and rivers. They prefer cool water, but can adjust to different temperatures, except for extreme cold. They need lots of oxygen in their water. To protect themselves from predators, crayfish are great at hiding under rocks, logs, inside vegetation or even under sand. Crayfish will consume (eat) plants and other dead organisms (plants and animals) in the water.

Although the crayfish are very adaptable, there are some things in the water that will destroy their habitat. Pollution can be harmful to crayfish, including chemicals, oil, and human waste. When humans share the water with crayfish, they can leave garbage and disrupt areas where female crayfish have laid eggs. That is why in some places, there are bans for people to fish and swim. Finally, because fishermen have equipment that help them catch many fish at once, this can kill too many crayfish and other fish.

In the classroom, we try to create a habitat for the crayfish that is close to its natural environment. We make little hiding places for the crayfish in the aquarium, provide it with plants to eat and fish to catch. It is also best to keep the water at room temperature or below, and to change the water at least once a week so that it's clean. The water should be filtered and oxygenated, because if the water does not have enough oxygen, the crayfish will drown. Finally, when changing the water, we let a bucket of water sit overnight, because this allows for the chlorine in the tap water to evaporate.

Aquatic (Water) Snails and Land Snails

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Face of an Aquatic Snail and Face of a Land Snail

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Internal and External Structures of a Land Snail

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Snails belong to a group of animals called mollusks, which have soft bodies. This group includes clams and oysters too. Because its body is soft and has no bones, it has a shell to protect it from predators. This shell is an example of an adaptation. An adaptation is a change by which an organism (living thing) becomes better suited for its environment. Snails have been around for approximately 600 million years ago, according to fossils found by scientists.

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Snail Fossil

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Snails can be found in gardens and in water. A snail likes moisture, darkness, and warm weather. In the winter, it hibernates underground. When the habitat is dry or the food is scarce, snails seal themselves off, with only a tiny hole to breathe. This is called estivation. It is like hibernation. The snail's metabolism slows down.


Land snails eat garden plants, fruits, and vegetables.


They usually live between 5-10 years, but sometimes longer.

Internal Structures of an Aquatic (Water) Snail

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Animals use their structures (body parts) to function (purpose) in the world. Each structure has one or more function to help the animal survive in its habitat. For example, the shell helps the snail protect itself from predators, and gives its a house in which to curl up and stay moist, when the weather is dry.

Snails are very strong, and call pull a load many times greater than their own mass (weight).

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Function of Structures

-Mouth: For eating and taking in oxygen from the water

-Gills: Used similarly to our lungs for breathing

-Eye: For seeing

-Nostrils: For smelling

Bess Beetle

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Insect Life Cycle

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1. Structures of Life Unit Summary

2. Video: Is it alive?

3. Video: From seed to flower

4. Article: Seeds Versus Eggs

5. National Geographic for Kids: Video on Lobsters

6. Video: Multicolored Mollusks

7. Crayfish Facts

8. Youtube Video of Snail Eating

9. National Geographic Video of Zombie Snail

10. Website on snails

11. Insect Life Cycle Video: Darkling Beetles

12. Insect Life Cycle Video: Indian Meal Moth

13. Dung Beetle Video

14. Hornworm Life Cycle Video

15. Gardener's Perspective on Hornworms