2nd Grade Science
How Do Organisms Change?
Unit 4
Unit 4: Stability and Change in Plants and Animals
Life Cycles
All plants and animals go through life cycles - series of stages of life.
Humans are an example! Our mothers get pregnant and give birth. We grow up from a baby, to a kid, to a teenager, and then to an adult. We keep aging until we eventually get old and die. These are the different stages of life: our life cycle. It's just the way life goes!
Plants
Plants have life cycles very different to animals. Let's take a look.
Pollination
Just like making new people, plants need a male and female to reproduce, or make new plants. The flower is the female. The pollen, or yellow powder located in the middle of the flower, is the male. They need to join forces to make a seed! But how does the pollen get to the flower? This process of pollen making its way to the flower is called pollination.
Unlike animals, plants can't move around. Because of this, they rely on moving things, like bees, butterflies, and birds to carry pollen from flower to flower. These moving beings also spread the seeds, so plants can grow. Wind can do this too, by blowing the seeds around!
When a seed falls on rich, healthy soil (because of wind, water, animals, etc), it's ready to start growing.
When the soil is perfect, and there's just the right amount of water, the seed begins to grow. The plant breaks through the shell of the seed and sprouts.
After some time, with lots of sunlight and water, the sprout grows into a full plant!
Try this activity to learn how a tomato plant grows!
Parts of a Plant
Plants have different parts that help them survive, grow, and produce more plants!
- Roots act like straws, helping the plant suck up water and nutrients from the soil. They also help hold the plant in place so it doesn't fall over.
- Stems are like the bodies of plants. Like pipes, they allow water and nutrients brought in by the roots to move through the plant.
- Leaves catch all the sunlight so the plant can make its own food.
- Flowers are where the pollen is located, so they are the reproductive part of the plant.
Animals
Animals can move, so their life cycles are much different.
Animals begin life from an egg or live birth. We, as humans, come from live birth. We grow up, mature into an adult, sometimes reproduce (make babies), and die. Every animal has its own special life cycle.
Let's look at a butterfly's life cycle!
The baby caterpillar hatches out of its egg. Now, it's ready to roam free!
Once it's fully grown, the caterpillar makes itself into a pupa - a casing or shell it stays in. While it's in there, its body is changing!
Finally, out comes a butterfly! This butterfly is now ready to fly away, feed on flowers, and mate with other butterflies.
Let's watch this happen in real life! Here's a super cool sped up video:
Changing the Environment
The environment is the area that surrounds a living thing - where it lives. Us living things change our environments in many different ways.
Home
Animals build their homes in their environment. Birds build nests from the branches and twigs around them, changing their environment.
Eating
Animals can change their environment by eating. A parrot eats seeds. When it poops them out, it helps the seeds grow in new places!
Growth
Sometimes the roots of plants can grow into cracks in rock or concrete. The roots can even make the cracks bigger, changing the environment.
Humans
We humans change our environment in many different ways, and a lot of times we hurt it. For example, when we build homes, we cut down trees for the empty space. But trees are super important! They clean our air and help us breathe. When we try to farm, sometimes we burn down plants and trees for the land.
