Living Things in the Biosphere

Living Things in the Biosphere

Middle School

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Learning Objectives

• Explain that all living things are made of one or more cells.

• Describe the functions of key cell parts, like the nucleus and mitochondria.

• Explain how scientists classify organisms based on shared evolutionary history.

• Explain how cells form tissues, organs, and organ systems.

Key Vocabulary

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Organism

An organism is a single living being that displays all the essential characteristics of life.

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Cell

The cell is the basic structural and functional unit of all living things, the smallest unit of life.

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Tissue

A tissue is a group of similar cells that work together to perform a specific, shared function.

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Organ

An organ is a distinct structure made of different types of tissues that work together for a purpose.

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Organ System

An organ system is a group of organs that cooperate to perform a major function in the body.

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Cell Membrane

The cell membrane is a protective layer that controls which substances are allowed to enter and leave a cell.

Key Vocabulary

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Cell Wall

The rigid outer layer of a plant cell that provides structural support and protection.

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Mitochondria

Often called the powerhouse of the cell, it converts food into usable energy.

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Homeostasis

The process by which an organism maintains a stable and balanced internal environment.

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Classification

The scientific method of grouping living things together based on their shared traits and similarities.

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Evolution

The gradual change in the characteristics of a species over many generations through natural selection.

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Anatomical Similarity

The likeness in physical body structures observed between different species, suggesting a common ancestor.

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Characteristics of Living Things

• All living things are made of one or more cells, the basic unit of life.

• Their cells contain water, carbohydrates, proteins, lipids, and nucleic acids like DNA.

• Organisms use energy to live, either by making their own food or eating others.

• They respond to their surroundings, grow, develop, and reproduce to create offspring.

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Multiple Choice

What is the basic unit that makes up all living things?

• A cell

• A protein

• A carbohydrate

• A nucleic acid

Multiple Choice

Which statement best explains the relationship between energy and the other characteristics of life?

• Energy is required for organisms to grow, respond to their surroundings, and reproduce.

• Energy is a type of cell found in all living things.

• Organisms create energy by responding to their surroundings.

• Reproduction is a process that uses up all of an organism's energy.

Multiple Choice

A scientist observes an object that grows larger over time and seems to react to light. What additional evidence is essential to conclude that the object is a living thing?

• Evidence that it is made of one or more cells.

• Evidence that it contains water.

• Evidence that it can move even faster.

• Evidence that it can grow even larger.

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Disproving Spontaneous Generation

Redi's Experiment

• Francesco Redi conducted a controlled experiment with meat in jars to test spontaneous generation in the 1600s.

• One jar was left open, allowing flies to land on the meat, while the other was sealed.

• Maggots, which are the young of flies, only appeared on the meat in the open jar.

Pasteur's Experiment

• Louis Pasteur used flasks with a special S-shaped neck to disprove spontaneous generation for microbes in the 1800s.

• The curved neck let air in but trapped airborne microorganisms like bacteria from reaching the broth.

• The broth only became cloudy with life when the flask's neck was broken, letting microbes enter.

Multiple Choice

What was the main scientific idea that both Francesco Redi and Louis Pasteur were testing with their experiments?

• To challenge the idea that living things can appear from nonliving matter.

• To prove that flies and microbes are dangerous to humans.

• To find a better way to store food for long periods.

• To show that air is made of tiny, invisible organisms.

Multiple Choice

How were the designs of Redi's sealed jar and Pasteur's S-shaped flask similar in their scientific function?

• They both prevented the entry of microorganisms from reaching the food source.

• They were designed to show that maggots and bacteria are the same.

• They proved that meat and broth will spoil even without air.

• They were used to trap and count the number of flies in an area.

Multiple Choice

Based on the principles from the experiments, what would most likely happen in Pasteur's experiment if the flask was tilted and some broth was trapped in the S-shaped neck, but the neck was NOT broken?

• The broth would become cloudy because life would be generated from the broth itself.

• The broth would remain clear because the S-shaped neck would trap the microbes from the air.

• The broth would become cloudy because breaking the neck lets in more heat.

• The broth would remain clear because microbes need light to grow.

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Needs of Living Things

• All living things need water for important jobs inside their cells.

• Living things get energy from food, either by making it or eating others.

• Every organism needs a home that provides shelter, food, and water.

• Living things must keep their internal conditions stable, like body temperature.

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Multiple Choice

What is the primary reason living things need water, food, a home, and stable internal conditions?

• To survive and carry out essential life functions.

• To help them move from one place to another.

• To allow them to grow as large as possible.

• To make them successful at competing with others.

Multiple Choice

What is the relationship between an organism's home and its need for food and water?

• A home provides an organism with access to food and water.

• Food and water are used by an organism to build its home.

• A home protects an organism from needing food and water.

• Organisms that have a home do not require food or water.

Multiple Choice

If a lizard that lives in a hot desert is moved to a cold, snowy mountain, what is the most immediate threat to its survival?

• Its inability to maintain a stable internal body temperature.

• The difficulty in finding the same types of food it used to eat.

• The challenge of finding a new source of fresh water.

• The lack of proper materials to build a familiar shelter.

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The Cell: A System of Parts

• A cell is a system where special structures called organelles perform specific jobs.

• The cell membrane is a boundary that controls what enters and leaves the cell.

• The nucleus is the cell's control center and directs all of its activities.

• Mitochondria are the 'powerhouses' that provide the cell with usable energy to live.

Multiple Choice

Which statement best describes a cell as a system?

• A system where different parts work together to perform specific jobs.

• A single part that does all the work for an organism.

• The part of an organism that only provides energy.

• The outer boundary that protects an organism.

Multiple Choice

How do the functions of the nucleus and mitochondria differ?

• The nucleus acts as the control center, while the mitochondria convert food into energy.

• The nucleus controls what enters the cell, while the mitochondria hold the genetic material.

• The nucleus provides energy, while the mitochondria serve as the control center.

• The nucleus is the outer boundary, while the mitochondria are the powerhouse.

Multiple Choice

If a cell's mitochondria stopped converting food into energy, what is the most likely consequence for the cell membrane's function?

• The cell membrane would not have the energy needed to control what moves in and out.

• The nucleus would take over the job of making energy.

• The cell's genetic material would be unable to give instructions.

• The cell would have no boundary to protect it from its environment.

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Levels of Organization

• Cells with similar jobs group together to form tissues, like muscle tissue.

• Different tissues work together to create an organ, such as the heart.

• Organs join to form an organ system, like the circulatory system.

• Organ systems work together to keep the organism alive and healthy.

Multiple Choice

What is formed when cells with a similar function group together?

• A tissue

• An organ

• An organ system

• An organism

Multiple Choice

What is the relationship between tissues and organs in a living organism?

• Different tissues work together to form an organ.

• Different organs work together to form a tissue.

• A single tissue is large enough to be an organ.

• An organ is another name for a group of cells.

Multiple Choice

A problem with the respiratory system can affect the entire body. What is the best explanation for this?

• Because organ systems must work together to keep the entire organism alive.

• Because the heart is a part of every organ system.

• Because tissues in one system can be replaced by tissues from another.

• Because a single organ failure does not affect the rest of the system.

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Classification and Evolution

• Organisms get a two-part scientific name, which includes their genus and species.

• The levels of classification are Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Organisms are grouped together based on sharing a common ancestor from the past.

• Similar bone structures in different animals suggest they share a common ancestor.

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Multiple Choice

What is the primary basis for grouping organisms together in the scientific classification system?

• They are grouped based on their diet.

• They are grouped based on their habitat.

• They are grouped based on sharing a common ancestor.

• They are grouped based on their body size.

Multiple Choice

An organism's two-part scientific name is composed of which two levels of classification?

• Kingdom and Phylum

• Family and Order

• Genus and species

• Domain and Kingdom

Multiple Choice

If a scientist finds that two different types of animals have very similar bone structures, what is the most logical conclusion they can draw?

• The two animals must live in the same environment.

• The two animals likely share a common ancestor.

• One animal must have evolved from the other one recently.

• The two animals must be members of the same species.

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Plant vs. Animal Cells

Plant Cells

• Have a rigid cell wall outside the cell membrane for structural support.

• Contain chloroplasts, which are the sites of photosynthesis to make their own food.

• Typically have one large central vacuole that is used for storing water.

Animal Cells

• Their outermost layer is a flexible cell membrane and they lack a cell wall.

• Do not have chloroplasts and get energy by consuming other living organisms.

• May have several small vacuoles for storage, but they are not always present.

Multiple Choice

What is a primary structural difference between plant cells and animal cells?

• Plant cells have a rigid cell wall, while animal cells do not.

• Animal cells have chloroplasts, while plant cells do not.

• Plant cells have a flexible cell membrane on the outside, while animal cells do not.

• Animal cells have one large vacuole, while plant cells have many small ones.

Multiple Choice

How does the method of obtaining energy differ between plant and animal cells?

• Plant cells use chloroplasts to make their own food, while animal cells consume other organisms for energy.

• Both cell types get energy by absorbing sunlight directly through the cell membrane.

• Animal cells store energy in a large central vacuole, while plant cells use chloroplasts.

• Plant cells get energy from water, while animal cells get energy from the air.

Multiple Choice

If a plant does not get enough water, its leaves and stem begin to wilt and droop. What is the most likely cellular explanation for this?

• The large central vacuoles in its cells lost water, causing the cells to lose their rigid structure.

• The cell walls in its cells became too flexible and could no longer provide support.

• The chloroplasts in its cells stopped working and could no longer produce energy.

• The small vacuoles in its cells absorbed too much water, causing the cells to swell.

Viruses and Bacteria

• Viruses are nonliving and need a host cell to multiply.

• Bacteria are living, single-celled organisms that can reproduce independently.

• While many bacteria are helpful, viruses cause diseases.

Multiple Choice

Which statement best describes a virus?

• It is a nonliving particle that requires a host to multiply.

• It is a living organism that can reproduce on its own.

• It is a helpful organism that lives in the human body.

• It is a single-celled organism that causes all diseases.

Multiple Choice

What is the main difference between how bacteria and viruses multiply?

• Bacteria are living and reproduce independently, while viruses are nonliving and need a host.

• Viruses are always helpful to humans, while bacteria always cause disease.

• Bacteria are complex multi-celled organisms, while viruses are single-celled.

• Viruses live in colonies, while bacteria always live alone.

Multiple Choice

A scientist discovers a new microorganism that is living, single-celled, and reproduces on its own. What is the most logical conclusion that can be made?

• The organism is likely a bacterium because it is a living, single-celled organism.

• The organism is definitely a virus because it is a microorganism.

• The organism could be either a virus or a bacterium.

• The organism is a virus because it will eventually cause a disease.

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Protists and Fungi

Protists

• Protists are eukaryotic organisms that are not classified as animals, plants, or fungi.

• They are a very diverse group and most are single-celled organisms that live in water.

• This group includes animal-like amoebas, plant-like algae, and fungi-like slime molds.

Fungi

• Fungi are eukaryotes with cell walls that get food by absorbing nutrients through hyphae.

• They can be decomposers that break down dead material, or they can be parasites.

• Fungi, like mushrooms, reproduce by releasing tiny spores from their fruiting bodies.

Multiple Choice

Which statement best describes the organisms classified as protists?

• A diverse group of eukaryotes that are not animals, plants, or fungi.

• Organisms that have cell walls and absorb food through hyphae.

• Multicellular organisms that reproduce using spores.

• A group of organisms that are all parasites.

Multiple Choice

What is the primary way that fungi, such as mushrooms, obtain their food?

• By absorbing nutrients from their surroundings using hyphae.

• By using sunlight to make their own food like plants.

• By hunting and consuming other small organisms.

• By releasing spores that turn into food.

Multiple Choice

A student finds an organism growing on a fallen log. It has a cell wall and appears to be breaking down the dead wood. Which piece of evidence would best confirm that this organism is a fungus and not a protist?

• If it releases spores to reproduce.

• If it is a single-celled organism.

• If it lives in a watery environment.

• If it is classified as an animal-like eukaryote.

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Common Misconceptions

Misconception	Correction
Viruses are living things.	Viruses are not alive and need a host cell to reproduce.
All bacteria are harmful.	Most bacteria are harmless and many are essential for life.
Fungi are a type of plant.	Fungi absorb food, while plants make their own.
Organs work in isolation.	Organs are part of systems that must work together to function.

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Summary

• All living things are made of cells, the basic unit of life.

• Cells group together to form tissues, organs, and organ systems.

• Plant cells have a cell wall and chloroplasts, but animal cells do not.

• Organisms are classified by evolutionary relationships and similar structures.

• The major groups of living things are bacteria, protists, fungi, plants, and animals.

• Viruses are nonliving and need to use a host cell to reproduce.

Poll

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

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