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Six Kingdoms of Life

Science, Grade 6

Six Kingdoms of Life

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Table Of Contents: Six Kingdoms of Life

1. Classification

2.1. Why Do Scientists Classify Organisms?
There are millions of types of organisms that live on Earth. A classification system helps scientists study, record and share information about organisms in a systematic and useful way.
2.2. How Are Organisms Classified?
The science of classification is called taxonomy. Organisms are classified according to shared characteristics such as cell structure, physical appearance, how they obtain food and method of reproduction.
2.3. DNA Technology and Classification
DNA technology is also playing a role in classification. The study of gene sequences and mutations has enabled scientists to understand the evolutionary relationships between different organisms.
2.4. Levels of Classification
There are seven levels of classification—kingdom, phylum, class, order, family, genus and species.
2.5. Scientific Name
Each organism is identified by its scientific name, which includes the genus and species. For example, humans are called Homo sapiens.

2. Six Kingdoms Overview

3.1. What Are the Six Kingdoms?
All organisms are classified into six different kingdoms—archaebacteria, eubacteria, protists, fungi, plants and animals.
3.2. Archaebacteria and Eubacteria
From an evolutionary perspective, archaebacteria and eubacteria are the simplest organisms, having evolved billions of years ago.
3.3. Protists
Protists are more complex organisms with a variety of characteristics. Scientists believe that protists evolved from bacteria.
3.4. Fungi, Plants and Animals
Fungi, plants and animals all evolved from different types of protists.

3. Archaebacteria and Eubacteria

4.1. Characteristics of Bacteria
Bacteria are simple unicellular organisms that can be found in nearly every environment on Earth. All bacteria are prokaryotic—they do not have a true nucleus or organelles with membranes.
4.2. Two Bacterial Groups
DNA studies suggest that there are two distinct groups of bacteria. Therefore bacteria are divided into two kingdoms—archaebacteria and eubacteria.
4.3. Where Are Archaebacteria Found?
Some archaebacteria are found in extreme environments, such as hot springs and salt lakes, while other species live in the ocean and soil.
4.4. Where Are Eubacteria Found?
Eubacteria are more common than archaebacteria and are found in soil, water and our bodies.
4.5. Beneficial and Harmful Bacteria
Archaebacteria and eubacteria are diverse kingdoms of organisms that contribute to oxygen production, food production, decomposition, medical applications and biotechnology. Some bacteria are harmful and cause disease.

4. Protists

5.1. Characteristics of Protists
Protists are eukaryotic organisms that have a true nucleus and membrane-bound organelles. They typically live in or near water and can be unicellular or multicellular.
5.2. Variety of Protists
The protist kingdom includes organisms that are not classified as plants, animals or fungi. Protists are difficult to categorize because there is a wide variation of characteristics among species.
5.3. Protist Groups
Protists are often grouped according to whether they are animal-like, plant-like or fungus-like.
5.4. Protozoa
Animal-like protists are known as protozoa. They are single-celled organisms that move to find food. Amoeba and paramecium are classified as protozoa.
5.5. Algae
Plant-like protists, called algae, contain chloroplasts and make their own food by the process of photosynthesis. They are primarily found in fresh water. Examples include volvox, euglena and spirogyra.
5.6. Fungus-Like Protists
Fungus-like protists are heterotrophs that feed on decomposing matter. They reproduce using spores. Water molds, downy mildew and slime molds are fungus-like protists.

5. Pause and Interact

6.1. Review
Use the whiteboard text tool to complete the activity.

6. Fungi

7.1. Characteristics of Fungi
Fungi are heterotrophic eukaryotes that absorb nutrients from decomposing matter. Most are multicellular, but some, like yeast, are unicellular.
7.2. Parts of a Fungus
The bodies of most fungi are composed of filaments called hyphae. These hyphae grow into a large mass of cells called mycelium.
7.3. Fungus Reproduction
Most fungi reproduce using spores. Fungi are classified into three groups according to their sexual reproductive structures—zygote, sac and club fungi.
7.4. Beneficial Fungi
Many fungi are beneficial organisms, contributing to the recycling of nutrients, food production and medical advances.
7.5. Harmful Fungi
There are some fungi that are harmful and cause disease in animals and plants.

7. Plants

8.1. Plant Characteristics
Plants are multicellular eukaryotes that live primarily on land. They are autotrophic, obtaining energy through photosynthesis.
8.2. Cellulose and Chloroplasts
Plant cells are distinct because they have cell walls composed of cellulose. Chloroplasts inside the cells contain the pigment chlorophyll that is needed for photosynthesis.
8.3. How Are Plants Classified?
Plants are classified according to whether they have vascular systems, produce seeds and develop flowers.
8.4. Nonvascular Plants
Nonvascular plants absorb water and nutrients directly from their surroundings. They are seedless and are considered to be the most ancient land plants. Examples include liverworts, mosses and hornworts.
8.5. Seedless Vascular Plants
Ferns, club mosses and horsetails are seedless vascular plants that reproduce using spores. The vascular tissues, xylem and phloem, carry water and nutrients throughout the plant.
8.6. Gymnosperms
Gymnosperms are vascular plants that produce seeds, but do not have flowers. The seeds of most gymnosperms develop in the scales of cones.
8.7. Angiosperms
Angiosperms are flowering vascular plants that produce seeds inside a fruit.

8. Pause and Interact

9.1. Review
Use the whiteboard tools to complete the activity.

9. Animals

10.1. Animal Characteristics
All organisms in the animal kingdom are multicellular heterotrophs, and their cells lack cell walls. Most animals reproduce sexually, have some type of nervous system and are capable of movement.
10.2. Major Animal Groups
There are over 1.5 million known species of animals. This branching tree shows how major animal groups are possibly related.
10.3. Invertebrates
Invertebrates are animals without backbones. These animals live in water and on land. They account for over 95% of the known animal species.
10.4. Invertebrate Groups
Some of the major groups of invertebrates include sponges, worms, mollusks, echinoderms, cnidarians and arthropods.
10.5. Vertebrates
Vertebrates have a spinal cord encased by protective vertebrae. They also have an endoskeleton that is composed of cartilage or bone. Fish, amphibians, reptiles, birds and mammals are all vertebrates.

10. Pause and Interact

11.1. Kingdom Identification
Drag and drop each organism into the correct kingdom.

11. Vocabulary Review

12.1. Six Kingdoms of Life Vocabulary Matching
All organisms in the animal kingdom are multicellular heterotrophs, and their cells lack cell walls. Most animals reproduce sexually, have some type of nervous system and are capable of movement.

12. Virtual Investigation

13.1. Classifying Organisms
In this virtual investigation you will classify several organisms according to their distinguishing characteristics. Use the information provided and your knowledge of the six kingdoms to help identify each organism.

13. Assessment

14.1. Six Kingdoms of Life