Domains and Kingdoms

Domains and Kingdoms

Middle School

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Learning Objectives

• Define what domains and kingdoms are and explain how they are different.

• Describe the three domains of life: Archaea, Bacteria, and Eukarya.

• Explain the main features scientists use to group different living organisms.

• Compare and contrast the four kingdoms in the Eukarya domain.

Key Vocabulary

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Prokaryotes

Simple cells that do not have a nucleus or other membrane-bound organelles inside them.

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Eukaryotes

Complex cells that contain a nucleus and other organelles enclosed within protective membranes.

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Autotrophs

These are organisms that create their own food, usually through the process of photosynthesis.

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Heterotrophs

Organisms that cannot produce their own food and must consume other living things to survive.

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Unicellular

A living organism that is composed of just one single cell for all its life functions.

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Multicellular

Complex organisms that are composed of many different types of cells, like plants and animals.

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Key Characteristics for Classification

• Cell structure: Organisms are grouped by having a nucleus (eukaryotes) or not (prokaryotes).

• Number of cells: An organism can be unicellular (one cell) or multicellular (many cells).

• Obtaining energy: Autotrophs make their own food, but heterotrophs must find their food.

• Reproduction: This process can be asexual (one parent) or sexual (two parents).

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Multiple Choice

A scientist is studying an organism that is unicellular and makes its own food. Based on these characteristics, which classification categories apply?

• Multicellular and Heterotroph

• Unicellular and Heterotroph

• Multicellular and Autotroph

• Unicellular and Autotroph

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Prokaryotic Domains: Archaea & Bacteria

Domain Archaea

• ​These are single-celled organisms that do not have a nucleus.

• ​​They often live in extreme places like hot springs or very salty water.

• ​Archae can be autotrophs or heterotrophs, making their own food or consuming others.

Domain Bacteria

• ​These are also single-celled organisms that do not contain a nucleus.

• ​​They are among the simplest and smallest organisms found on our planet.

• ​Bacteria can be autotrophs or heterotrophs, making their own food or consuming others.

Multiple Choice

What is a key difference between organisms in Domain Archaea and Domain Bacteria?

• Bacteria are multicellular, while Archaea are unicellular.

• Archaea are found in extreme environments.

• Archaea have a nucleus, while Bacteria do not.

• Archaea are autotrophs, while Bacteria are only heterotrophs.

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Domain Eukarya

• Eukaryotic cells have a nucleus and other membrane-bound organelles, making them complex.

• They can reproduce asexually through mitosis or sexually through meiosis.

• This domain includes single-celled organisms and complex ones like plants and animals.

• Eukarya is divided into four kingdoms: Protista, Fungi, Plantae, and Animalia.

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Multiple Choice

Which of the following is a defining characteristic of all organisms in Domain Eukarya?

• They are all multicellular.

• Their cells contain a nucleus.

• They all make their own food.

• They only reproduce asexually.

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Kingdoms Protista and Fungi

Kingdom Protista

• Protists are eukaryotes, and most are unicellular, meaning they are single-celled organisms.

• This kingdom includes a diverse group of organisms such as algae and slime molds.

• Some protists are autotrophs, which means they can produce their own food like plants.

Kingdom Fungi

• Fungi are also eukaryotes, but they are mostly multicellular, like mushrooms and molds.

• They are heterotrophs and act as decomposers, feeding on dead plants and animals.

• Fungi reproduce by releasing tiny spores that can grow into new organisms.

Multiple Choice

How do organisms in Kingdom Fungi obtain their energy?

• They hunt and consume other living organisms.

• They act as decomposers, feeding on dead organic matter.

• They perform photosynthesis to make their own food.

• They are all unicellular autotrophs.

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Kingdoms Plantae and Animalia

Kingdom Plantae

• ​These are multicellular organisms like trees, flowers, and even vegetable plants.

• ​​They are autotrophs, which means they make their own food using photosynthesis.

• ​Most plants cannot move from one place to another on their own.

Kingdom Animalia

• ​This kingdom includes all multicellular living things, from small insects to humans.

• ​​They are heterotrophs, so they get energy by eating other living things.

• ​Most animals have the ability to move around and reproduce sexually.

Multiple Choice

A key distinction between Kingdom Plantae and Kingdom Animalia is:

• Plantae are autotrophs, while Animalia are heterotrophs.

• Plantae reproduce asexually, while Animalia reproduce sexually.

• Plantae are mobile, while Animalia are immobile.

• Plantae are unicellular, while Animalia are multicellular.

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Common Misconceptions about Microbes

Misconception	Correction
Fungi are a type of plant.	Fungi are decomposers, while plants make their own food.
All single-celled organisms are bacteria.	Single-celled organisms are also found in Archaea and Protista.
All microbes are germs that cause disease.	Many microbes are beneficial and essential for ecosystems.

Multiple Choice

Why are organisms in Domain Eukarya generally considered more complex than those in Domain Archaea and Domain Bacteria?

• Because they are all multicellular.

• Because they are all heterotrophs.

• Because they only live in extreme environments.

• Because their cells have a nucleus and membrane-bound organelles.

Multiple Choice

A newly discovered organism is multicellular, cannot move, and performs photosynthesis. How would you classify this organism?

• Kingdom Animalia

• Kingdom Plantae

• Kingdom Fungi

• Kingdom Protista

Multiple Choice

A scientist discovers a new single-celled organism in a deep-sea vent. It has no nucleus. What is the most likely domain for this organism, and why?

• Domain Bacteria, because all single-celled organisms are bacteria.

• Kingdom Fungi, because it is a decomposer.

• Domain Archaea, because it lives in an extreme environment.

• Domain Eukarya, because it is a newly discovered organism.

Multiple Choice

Analyze the primary role of Kingdom Fungi within an ecosystem. What would be a likely outcome if all fungi were to disappear?

• Dead organic matter would accumulate, and nutrient recycling would decrease significantly.

• Animals would lose their ability to move.

• Plants would have no source of food.

• The amount of oxygen in the atmosphere would decrease.

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Summary

• Living things are organized into large groups called Domains and smaller groups called Kingdoms.

• The three domains are Archaea, Bacteria, and Eukarya, separated by their cell structure.

• Domain Eukarya includes the kingdoms Protista, Fungi, Plantae, and Animalia.

• Plantae are producers that make their own food, while Fungi and Animalia are consumers.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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