Life Science Unit (Book)
| Site: | Learnbps |
| Class: | Grade 4 Life Science Commons |
| Book: | Life Science Unit (Book) |
| Printed by: | Guest user |
| Date: | Sunday, December 22, 2024, 3:39 PM |
Life Science Unit
Life Science Unit
Biology is the study of life, so the Life Sciences are essentially, the study of biology.
You will be studying all types of living things. Branches of the life sciences study things from the tiniest microorganisms to the largest plants and animals.
Standards
Science Standards
From Molecules to Organisms: Structures and Processes
Students who demonstrate understanding can:
- SCI-04.LS1.01 Construct an argument that plants and animals have internal and external structures that function to support
survival, growth, behavior, and reproduction.
Science and Engineering PracticesSEPs7: Engaging in Argument from EvidenceDisciplinary Core IdeasSCI-04.LS1: Structure and FunctionCrosscutting ConceptsCCCs4: Systems and System Models
- SCI-04.LS1.02 Form an explanation to describe that animals receive different types of information
through their senses, process the information in their brain, and respond to the information in different ways.
Science and Engineering PracticesSEPs6: Constructing Explanations and Designing SolutionsDisciplinary Core IdeasSCI-04.LS1: Structure and FunctionCrosscutting ConceptsCCCs2: Cause and Effect
ND Standards Connections
ELA/Literacy
ELA-04.W.01 Write opinion pieces on topics or texts, supporting a point of view with reasons and information
Mathematics
MAT-04.G.03 Recognize a line of symmetry for a two-dimensional figure as a line across the figure such that the figure can be folded along the line into matching parts. Identify line-symmetric figures and draw lines of symmetry.
Introduction to Plants
It's your grandmother's birthday today. Tonight your parents are having a party for her. Everyone is helping out, even you. The table needs to be set with dinnerware. Mom is making your grandmother's favorite meal. You are helping by picking up your things and putting them away. You are almost finished when the doorbell rings. You run to the door to answer and there stands friends of your grandmother. They are here for the party.
You notice one person holding cut flowers. Another person is holding a plant. Flowers and plants are a common gift in our society.You are thinking that you would rather have a video game. Why are flowers and plants so important to us? Sure, they look nice. Might there be some other reasons? Perhaps!
Lesson Objectives
- Describe plants, their needs, and their importance.
- Describe the structure and function of roots, stems, and leaves.
Lesson Vocabulary
- leaf
- plant
- root
- stem
What Are Plants?
Plants are not like animals. Plants cannot move to find food. Instead, they must have the ability to survive where they are. They also must have the ability to make their own food. They also cannot move around to find a mate, so they have evolved unique ways to reproduce.
Needs of Plants
Plants are somewhat limited by temperature in terms of where they can grow. They need temperatures above freezing. The can survive temperatures below freezing, but cannot grow during this period of time. They also need light, carbon dioxide, and water. These are the ingredients they need to make their own food. Like most other living things, plants need oxygen. Oxygen is required for cellular respiration. In addition, plants need minerals. The minerals are required to make proteins and other organic molecules.
Importance of Plants
Life as we know it would not be possible without plants. Why are plants so important?
- Plants supply food to nearly all land organisms, including people. We mainly eat either plants or other living things that eat plants.
- Plants produce oxygen. Oxygen is needed by almost all the Earth's organisms.
- Plants absorb carbon dioxide from the air. This helps control the greenhouse effect and global warming.
- Plants recycle matter in ecosystems. For example, they are an important part of the water cycle. They take up liquid water from the soil through their roots. They release water vapor to the air from their leaves.
- Plants provide many products for human use. They include timber, medicines, dyes, oils, and rubber.
- Plants provide homes for many other living things. For example, a single tree may provide food and shelter to many species of animals.
Plant Structures
Most modern plants have several structures that help them survive and reproduce. Major structures of most plants include roots, stems, and leaves.
Roots
Roots are important organs in most modern plants. There are two types of roots. First, there are the primary roots, which grow downward. Secondly, there are the secondary roots. These roots branch out to the sides. Together, all the roots of a plant make up the plant's root system. Figure below shows two different types of plant root systems. A taproot system has a very long primary root, called a taproot. A fibrous root system has many smaller roots and no large, primary root.
The roots of plants have three major jobs.
- They must absorb water and minerals, anchor and support the plant, and store food. Roots have special features that are well suited to absorb water and dissolved minerals from the soil.
- Root systems help anchor plants to the ground. They allow plants to grow tall without falling over.
- In many plants, roots store food produced by the leaves. This process is called photosynthesis.
Two types of root systems
Stems
Stems are organs that hold plants upright. They allow plants to get the sunlight and air they need. Stems also bear leaves, flowers, cones, and smaller stems. These structures grow at points called nodes. The stem between nodes is called an internode. (See Figure.) Nodes and internodes of a stem Nodes and internode of a stem
Stems are needed for transport and storage. They carry water and minerals from roots to leaves. It carries dissolved sugar from the leaves to the rest of the plant. The stem is like an elevator for the plant. The stem allows movement from the top of the plant to the bottom and vice versa. Without this connection between roots and leaves, plants could not survive. In many plants, stems also stores food or water during cold or dry seasons.
Leaves
Leaves are the keys not only to plant life but to virtually all life on land. The primary role of leaves is to collect sunlight. This sunlight is needed for the plant to make food. Leaves vary in size, shape, and how they are arranged on stems. You can see examples of different types of leaves in Figure.
Plant leaves come in a variety of shapes and sizes
Variation in plant leaves
Each type of leaf is well suited for the plant's environment. It maximizes light exposure while conserving water. They are also reduces wind resistance. Leaves also benefit the plant in some other way in its particular habitat. For example, some leaves are divided into many smaller leaflets. This reduces wind resistance and water loss.
Leaves are basically factories for photosynthesis.
- A factory has specialized machines to produce a product. In a leaf, the "machines" are the chloroplasts.
- A factory is connected to a transportation system that supplies it with raw materials and carries away the finished product. In a leaf, transport is carried out by veins containing vascular tissue. Veins carry water and minerals to the cells of leaves. They carry away dissolved sugar.
- A factory has bricks, siding, or other external protection. A leaf is covered with dermal cells. They secrete waxy cuticle to prevent evaporation of water from the leaf.
- A factory has doors and windows to let some materials enter and leave. The surface of the leaf has tiny pores called stomata (stoma, singular). They can open and close to control the movement of gases between the leaves and the air.
What is Photosynthesis?
If a plant gets hungry, it cannot walk to a local restaurant and buy a slice of pizza. So, how does a plant get the "food" it needs to survive? Plants are producers, which means they are able to make, or produce, their own "food." They also produce the "food" for other organisms. Plants collect the energy from the sun and turn it into special chemicals. Using the energy from the sun, they produce the special chemicals using air, water and nutrients from the soil. So once again, how does a plant get the food it needs to survive? The plants is able to make its own "food" from the sun's energy, carbon dioxide from the air, and water.
Actually, almost all organisms obtain their energy from plants. For example, if a bird eats a caterpillar, then the bird gets the energy that the caterpillar. The caterpillar gets its energy from the plants it eats. So the bird indirectly gets energy from the plant. Therefore, the process of photosynthesis is central to sustaining life on Earth.
Review
Lesson Summary
- Plants feed most other organisms. They also perform many other services.
- Three organs (structures) commonly found in modern plants are roots, stems, and leaves.
Lesson Review Questions
- What are plants? What do plants need?
- How do plants grow?
- Outline the general life cycle of a plant.
Apply Concepts - Choose one of the three main organs of plants: roots, stems, or leaves. State the primary function of the organ, and then explain how the organ's structure suits it for its function.
Think Critically - Why would life as we know it be impossible without plants?
Plant Reproduction
So what exactly is a flower?
This view is of a beautiful Prairie Rose flower. Notice the fine detail. There is a reason why this flower looks like it does. Do you know why flowers so colorful? What is the purpose of all the parts?
Lesson Objective
Identify processes of sexual reproduction in flowering plants, including pollination, fertilization (seed production), seed dispersal, and germination.
Lesson Vocabulary
- reproduction
- pollination
- pollen
- fertilization
- seed dispersal
Flowering Plants
Flowering plants evolved millions of years ago. Unlike animals, there are no boy or girl plants. Plants have both male and female parts. That does not mean that plants do not need help to reproduce.
Some plants form seeds. These are called flowering seed plants. The seeds form in the plant's ovaries. A plant's fruit may fall to the ground and start to grow. A plant's fruit may get eaten by animals. If eaten, the seeds of the fruit are passed through the animal's digestive tract. As the animal eliminates its waste, the seeds are spread around. Because animals do not stay in one place, they help the plant populate a bigger area. The animal gets a tasty treat and helps the plant reproduce.
The ovaries are just one of the structures of a plant. The flower's job is to attract animals, such as bees and birds. The animals are able to spread the pollen to other plants. Animals are needed to get the pollen from the male to the female parts of the plant. It is important for diversity that the pollen is passed from one plant to another.
Parts of a Flower (Filter)
Flowers have both male and female reproductive parts. The main parts of a flower are shown in Figure below. They include the stamen, pistil, petals, and sepals.
A flower includes both male and female reproductive structures.
The stamen is the male reproductive structure of a flower. It consists of a stalk-like filament. At the end of the filament is the anther. The anther contains pollen sacs. It is here the pollen grains form. The filament raises the anther up high. This helps the pollen to be more likely to be carried away. It may blow in the wind. It may be picked up by an animal and carried away. Many animals are pollinators. A pollinator is any animal who carries the pollen from one plant to another.
The pistil is the female reproductive structure of a flower. It consists of a stigma, style, and ovary. The stigma is raised. It is also sticky to help catch pollen. The style supports the stigma and connects it to the ovary. The ovary contains the egg.
Petals attract animals to the flower. Petals are often brightly colored. Bright colors make them easier for animals to see.
Sepals protect the developing flower while it is still a bud. Sepals are usually green. Sepals camouflage the bud from animals that may eat it for food.
Parts of a Flower (Embed)
Flowers have both male and female reproductive parts. The main parts of a flower are shown in Figure below. They include the stamen, pistil, petals, and sepals.
A flower includes both male and female reproductive structures.
The stamen is the male reproductive structure of a flower. It consists of a stalk-like filament. At the end of the filament is the anther. The anther contains pollen sacs. It is here the pollen grains form. The filament raises the anther up high. This helps the pollen to be more likely to be carried away. It may blow in the wind. It may be picked up by an animal and carried away. Many animals are pollinators. A pollinator is any animal who carries the pollen from one plant to another.
The pistil is the female reproductive structure of a flower. It consists of a stigma, style, and ovary. The stigma is raised. It is also sticky to help catch pollen. The style supports the stigma and connects it to the ovary. The ovary contains the egg.
Petals attract animals to the flower. Petals are often brightly colored. Bright colors make them easier for animals to see.
Sepals protect the developing flower while it is still a bud. Sepals are usually green. Sepals camouflage the bud from animals that may eat it for food.
Flowers and Pollinators
Some flowers may have bright colors. Others may have strong scents. Some may have sweet nectar. All these traits help to attract animals. Why do you think it is important to attract animals? Animals are able to carry around pollen from one plant to another. The animals they attract may include insects, birds, mammals, and even reptiles. While visiting a flower, an animal picks up pollen from the anthers. The animal then travels to another flower. While there, some of the pollen brushes off on the stigma. This allows cross-pollination. By spreading pollen to different plants, it helps increase plant diversity.
Brightly colored fruits attract animals that may disperse their seeds. It’s hard to miss the bright red apples on these trees.
Evolution of Flowering Plants
Flowering plants have been around for a really long time. Scientists think they evolved over 200 million years ago. Fossil flowers have male and female reproductive organs just like today. There have been changes over time as plants evolved new and better traits to help them reproduce. From fossil evidence, the ancient plants did not have petals or sepals as they do today.
Just like now, the earliest flowers most likely attracted insects and other animals. The insects and animals spread the pollen from flower to flower. This was a big help to flowers. Animals can be better than the wind at carrying pollen. Wind-spread pollen may or may not land on another flower. To take better advantage of this “animal labor,” plants evolved certain traits. These traits can include brightly colored petals, strong scents, and sweet nectar. These are all traits that help attract animals. The flowers are able to move around their pollen. The animals get a free meal.
Other plants developed additional traits that helped them reproduce.
Some plants rely on seeds getting stuck in animal fur. Once stuck, the seeds are carried off to another location. Eventually, the seeds fall off.
Other plants developed traits to better disperse their seeds using the wind. With time, plants develop better and better traits to help them reproduce.
Developing Specialized Traits
Relying on an animal to come by is risky. A flower may have to wait a long time for the right animals to come by. What if one never passes close enough to the flower?
Hoping the wind will blow is also risky for a plant. What if the wind does not blow? What if the blowing pollen does not land on another flower? The wind could even blow the pollen over the ocean where it is wasted.
Giving free nectar is costly. It is not a good use of the plant's energy. A plant uses a lot of energy to produce nectar. Some animals may just drink the nectar. They may not carry off any pollen in return. To improve their chances, plants evolved special traits. For example, they developed ways to “hide” their nectar. Only certain animals were able to get at the plant's hidden nectar. These specific animals might be more likely to visit only flowers of the same species. This was also a benefit for some animals. Animals also evolved special traits to get to the nectar. This is called co-evolution of traits.
Two examples of this type of co-evolution are shown in Figure below.
The hummingbird has a long narrow bill. The long narrow bill enables it to reach nectar at the bottom of the tube-shaped flowers. The bat is active at night. Bright white, night-blooming flowers attract it. In each case, the flowering plant and its animal co-evolved. They have become better suited for their roles.
Review
Lesson Summary
- Most modern seed plants produce seeds in the ovaries. Ovaries may develop into fruits.
- Flowers attract pollinators and fruits are eaten by animals. Both traits aid the dispersal of seeds.
Lesson Review Questions
Recall
- Describe the male and female reproductive structures of flowers and their functions.
- State how fruits help flowering plants reproduce.
- Explain how flowering plants and their animal pollinators co-evolved.