Diversity of Life

Diversity of Life

Middle School

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Learning Objectives

• Provide evidence that all living things are composed of one or more cells.

• Describe the functions of organelles and differentiate between plant and animal cells.

• Compare how sexual and asexual reproduction affect the genetic variation of offspring.

• Explain how structures and behaviors help plants and animals successfully reproduce.

• Explain how genetic and environmental factors influence the growth of an organism.

Key Vocabulary

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Cell

The basic structural and functional unit of all known living organisms, often called life's building blocks.

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Unicellular Organism

A living being that is made of only one single cell, carrying out all life processes.

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Multicellular Organism

A complex living being that consists of many different types of specialized cells working together.

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Prokaryote

A simple, single-celled organism that does not have a membrane-bound nucleus or other specialized organelles.

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Eukaryote

An organism whose cells contain a true nucleus and other membrane-bound organelles with specialized functions.

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Organelle

A specialized structure found inside a eukaryotic cell that performs a specific, vital job or function.

Key Vocabulary

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Cell Membrane

The cell membrane is a protective layer that controls what substances can enter or leave the cell.

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Cell Wall

The cell wall is a rigid outer layer that provides structural support and protection to plant cells.

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Asexual Reproduction

Asexual reproduction involves a single parent, resulting in offspring that are genetically identical to that parent.

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Sexual Reproduction

Sexual reproduction combines genetic material from two parents to produce genetically unique offspring, creating genetic variation.

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Genetic Variation

Genetic variation refers to the differences in the genetic makeup of individuals within a particular population.

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Heredity

Heredity is the process by which genetic traits are passed down from parents to their offspring.

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What is Life? The Cell Theory

Unicellular

• An organism that is made up of only a single cell.

• The single cell carries out all the essential functions of life.

• They are microscopic and cannot be seen with the unaided eye.

Multicellular

• An organism that is made up of many different types of cells.

• Different cells are specialized to perform specific functions for the organism.

• Most of these complex organisms are visible to the unaided eye.

Multiple Choice

What is the defining characteristic of a unicellular organism?

• It is made up of only a single cell that performs all functions.

• It is part of a larger, more complex organism.

• It can only be found in water.

• It does not need to perform any functions to live.

Multiple Choice

What is a key difference in how unicellular and multicellular organisms are structured?

• Unicellular organisms are always larger than multicellular ones.

• In multicellular organisms, different cells have specialized jobs.

• Only unicellular organisms can be seen with the unaided eye.

• Multicellular organisms have only one type of cell.

Multiple Choice

A scientist discovers a new organism that is large enough to be seen without a microscope. Based on this observation, what can the scientist most likely conclude?

• It is likely a multicellular organism with specialized cells.

• It must be a type of unicellular organism.

• It does not have any cells.

• It has one large cell that performs all of its functions.

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Types of Cells: Prokaryotes vs. Eukaryotes

Prokaryotic Cells

• ​These are simple, single-celled organisms such as bacteria.

• ​​Their most important feature is that they do not have a nucleus.

• ​The cell's genetic material is located in the cytoplasm.

Eukaryotic Cells

• ​These are the more complex cells that make up plants and animals.

• ​​They have a true nucleus, which contains the cell's genetic material.

• ​They also contain many other specialized structures called organelles.

Multiple Choice

What is the main structural difference between prokaryotic and eukaryotic cells?

• The presence of a nucleus in eukaryotic cells.

• The size of the cell.

• The type of genetic material.

• The location of the cytoplasm.

Multiple Choice

What is the relationship between the nucleus and the location of genetic material in a simple, single-celled organism like bacteria?

• It is found in the cytoplasm because there is no nucleus.

• It is stored in specialized structures called organelles.

• It is attached to the outside of the cell.

• It does not have any genetic material.

Multiple Choice

A scientist observes a cell that contains its genetic material inside a nucleus and has many other specialized organelles. What conclusion can be drawn about this cell?

• It is a prokaryotic cell, like bacteria.

• It is a eukaryotic cell, like those found in plants or animals.

• It is a simple cell with no specialized structures.

• It is a cell that does not have a nucleus.

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Inside the Cell: Structures and Functions

Plant Cells

• Plant cells have a rigid cell wall that provides structural support to the entire cell.

• They contain special organelles called chloroplasts, which are the sites of photosynthesis for food production.

• The nucleus is an organelle that contains all of the cell’s genetic information.

Animal Cells

• Animal cells are enclosed by a flexible cell membrane, controlling what enters and exits the cell.

• Unlike plant cells, animal cells do not have a cell wall or chloroplasts.

• Both cell types have mitochondria to release energy for the cell through cellular respiration.

Multiple Choice

What is the primary function of the cell wall in a plant cell?

• To provide structural support to the cell

• To control what enters and exits the cell

• To produce food through photosynthesis

• To release energy for the cell to use

Multiple Choice

How can you distinguish a plant cell from an animal cell based on their structures?

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

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

• Plant cells have a cell membrane, while animal cells have a cell wall.

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

Multiple Choice

A scientist observes a cell that has a nucleus, mitochondria, and a cell membrane, but it does not have a cell wall or chloroplasts. What is the most logical conclusion about this cell?

• It is an animal cell because it lacks a cell wall and chloroplasts.

• It is a plant cell because it has a nucleus and mitochondria.

• It is an animal cell because it has a nucleus and mitochondria.

• It is a plant cell because it has a cell membrane.

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What Are Bacteria?

• Bacteria are single-celled living things known as prokaryotes.

• They reproduce by splitting into two identical cells through binary fission.

• While some cause illness, most bacteria are helpful to us and ecosystems.

• They help with digestion, decomposition, and making food and medicines.

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Multiple Choice

Which statement best describes bacteria?

• They are single-celled living things known as prokaryotes.

• They are multi-celled organisms that cause illness.

• They are non-living particles that need a host to reproduce.

• They are plant cells that perform photosynthesis.

Multiple Choice

How do bacteria create more of themselves?

• They reproduce by splitting into two identical cells.

• They combine with other cells to form a new organism.

• They lay eggs that hatch into new bacteria.

• They transform into a different type of cell.

Multiple Choice

If a single helpful bacterium that aids in digestion undergoes binary fission, what is the most likely outcome?

• The number of helpful bacteria would increase, aiding digestion.

• The bacteria would become harmful and cause illness.

• The two new cells would be different from the original cell.

• The bacteria would stop reproducing and be destroyed.

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What Are Viruses?

• Viruses are infectious agents that are not made up of cells.

• They have genetic material (DNA or RNA) inside a protein coat.

• Viruses must invade a host cell to make copies of themselves.

• They show both living and non-living characteristics, putting them on the edge of life.

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Multiple Choice

What is a fundamental characteristic of viruses?

• They are a type of bacteria.

• They are not made up of cells.

• They can make their own food.

• They have a nucleus and mitochondria.

Multiple Choice

Why does a virus need to invade a host cell?

• To feed on the host cell's nucleus for energy.

• To use the host cell's resources to make copies of itself.

• To hide from the host's immune system.

• To steal the host cell's protein coat.

Multiple Choice

Which statement best explains why viruses are considered to be on the 'edge of life'?

• They have genetic material but cannot reproduce on their own.

• They are infectious agents that are not made of cells.

• They have a protein coat that protects their genetic material.

• They can cause common illnesses in many different organisms.

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Plant Biology: Energy and Transport

Energy Production

• ​Plants create their own food, a sugar called glucose, through the process of photosynthesis.

• ​​This process uses light, water, and carbon dioxide, and it takes place in the chloroplasts.

• ​The simplified chemical equation is: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Energy Use & Transport

• ​Cellular respiration releases energy from glucose and occurs in the mitochondria of plant and animal cells.

• ​​The equation is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.

• ​Xylem moves water to the leaves, while phloem moves the glucose (sugar) to the rest of the plant.

Multiple Choice

What is the primary purpose of photosynthesis in plants?

• To create glucose, a type of sugar for food

• To release energy from sugar in the mitochondria

• To move water from the roots to the leaves

• To absorb nutrients directly from the soil

Multiple Choice

What is the relationship between photosynthesis and cellular respiration in a plant cell?

• Photosynthesis produces sugar and oxygen, which are then used by cellular respiration to produce energy.

• Cellular respiration produces water and light, which are then used by photosynthesis to create sugar.

• Photosynthesis and cellular respiration both occur in the chloroplasts to produce energy for the plant.

• Cellular respiration happens in plants, while photosynthesis happens in animals.

Multiple Choice

If a plant's phloem tissue were damaged, what would be the most likely consequence?

• The glucose made in the leaves could not be transported to the roots and stem for energy.

• The water needed for photosynthesis could not travel from the soil to the leaves.

• The plant would be unable to take in carbon dioxide through its leaves.

• The mitochondria would be unable to perform cellular respiration.

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Plant Reproduction and Dispersal

Reproduction

• ​Flowering plants use specialized structures to help them reproduce successfully.

• ​​Pollination, the transfer of pollen to the stigma, is a crucial first step.

• ​Flowers use their unique colors, scents, and shapes to attract specific pollinators.

Seed Dispersal

• ​After fertilization, the flower's ovule develops into a seed containing the embryo.

• ​​The ovary grows into a fruit, which protects the seed and helps it travel.

• ​Seeds are spread to new places by wind, water, or by hitching rides on animals.

Multiple Choice

What is pollination?

• The transfer of pollen to the stigma.

• The development of a seed inside a fruit.

• The spreading of seeds to new locations.

• The growth of a flower's colorful petals.

Multiple Choice

What is the primary relationship between a flower's unique colors and scents and the plant's life cycle?

• To protect the plant from being eaten by animals.

• To attract specific pollinators needed for reproduction.

• To help the plant absorb sunlight for energy.

• To provide a protective covering for the seeds.

Multiple Choice

If a flowering plant that relies on animals for seed dispersal were introduced to an island with no animals, what would be the most likely outcome?

• The plant's flowers would be unable to produce any pollen.

• The plant's seeds would likely not be carried to new locations to grow.

• The plant would not be able to develop a protective fruit around its seeds.

• The plant's ovule would be unable to develop into an embryo.

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Animal Behavior for Reproduction

Courtship Dances

• Animals use specific behaviors to find a mate and reproduce.

• For instance, many birds perform complex courtship dances to attract a partner.

• These displays demonstrate the male bird's health and suitability as a mate.

Chemical Signals

• Insects often use chemical signals called pheromones to find each other.

• A moth can release these pheromones to attract a mate from far away.

• This greatly increases their chances of successful reproduction in a large area.

Multiple Choice

What is the main reason animals like birds and moths use behaviors such as courtship dances and chemical signals?

• To find a mate and successfully reproduce

• To compete with other animals for food

• To protect themselves from predators

• To establish dominance over other animals

Multiple Choice

How does the method a bird uses to attract a mate differ from the method a moth uses?

• A courtship dance is a visual signal, while a pheromone is a chemical signal.

• A courtship dance is used by insects, while pheromones are used by birds.

• A courtship dance signals health, while a pheromone signals danger.

• A courtship dance is for finding food, while a pheromone is for mating.

Multiple Choice

If an animal needs to find a mate in a wide, open grassland where individuals are spread far apart, which strategy would be most effective and why?

• Releasing chemical signals, because they can attract mates over a long distance.

• Performing a complex dance, because it is a more impressive display.

• Creating a colorful display, because it is easier to see in a large area.

• Making a loud noise, because sound travels farther than chemicals.

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Reproduction and Genetic Variation

Asexual Reproduction

• Asexual reproduction involves only one parent, which passes all its genes to the offspring.

• The resulting offspring are genetically identical to the parent and to each other.

• This method of reproduction does not create new genetic variation within a population.

Sexual Reproduction

• Sexual reproduction involves two parents, each contributing half of the genes to the offspring.

• The offspring has a new, unique combination of genes, different from both parents.

• This process is a major source of genetic variation within a population.

Multiple Choice

What is the primary difference between asexual and sexual reproduction?

• Asexual reproduction involves one parent, while sexual reproduction involves two parents.

• Asexual reproduction creates genetic variation, while sexual reproduction does not.

• Asexual reproduction results in unique offspring, while sexual reproduction results in identical offspring.

• Asexual reproduction occurs in animals, while sexual reproduction occurs in plants.

Multiple Choice

How does the genetic makeup of offspring differ between asexual and sexual reproduction?

• Offspring from asexual reproduction are genetically identical to the parent, while offspring from sexual reproduction have a unique combination of genes.

• Offspring from asexual reproduction are always larger than the parent, while offspring from sexual reproduction are smaller.

• Offspring from asexual reproduction have more genes than the parent, while offspring from sexual reproduction have fewer.

• Offspring from asexual reproduction are genetically different from the parent, while offspring from sexual reproduction are identical to one parent.

Multiple Choice

If a new, deadly disease were introduced to a population, which method of reproduction would give the population a better chance of survival and why?

• Sexual reproduction, because it creates genetic variation which increases the chance that some individuals will have traits to survive the disease.

• Asexual reproduction, because it is a faster process that can create more offspring quickly to fight the disease.

• Asexual reproduction, because all the offspring will be identical and therefore equally strong against the disease.

• Sexual reproduction, because it requires two parents to protect the offspring from the disease.

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Factors Influencing an Organism's Growth

Genetic Factors

• These are instructions for growth that an organism inherits from its parents through genes.

• For instance, specific genes determine whether a pea plant is naturally a tall or dwarf variety.

• These factors determine the potential an organism has for traits like height and overall structure.

Environmental Factors

• These are external conditions from the surroundings that impact how an organism can grow.

• Key factors include the availability of sunlight, water, essential nutrients, and adequate living space.

• Good conditions help an organism reach the full growth potential that is set by its genes.

Multiple Choice

What are the two primary types of factors that together determine how an organism will grow?

• Genetic and environmental factors

• Sunlight and water availability

• Inherited and learned traits

• Tall and dwarf varieties

Multiple Choice

What is the relationship between an organism's genetic factors and its environmental factors?

• Environmental factors can limit or support the expression of an organism's genetic potential.

• Genetic factors are solely responsible for an organism's final size and structure.

• Environmental conditions can change an organism's inherited genes.

• Genetic and environmental factors operate independently and do not influence each other.

Multiple Choice

A specific pea plant has genes that give it the potential to grow very tall. If this plant is grown in a small pot with little water or sunlight, what is the most likely outcome?

• The plant will likely be shorter than its genetic potential due to poor environmental conditions.

• The plant is guaranteed to grow tall because its genes determine its height.

• The plant's genes will change to a dwarf variety to match the environment.

• The plant will grow taller than usual to try and find more sunlight.

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Common Misconceptions

Misconception	Correction
Viruses are a type of simple cell.	Viruses are not cells; they need a host cell to reproduce.
Plants only perform photosynthesis.	Plants use photosynthesis to make food and respiration to release energy.
Offspring are always exact copies of their parents.	Asexual reproduction makes copies; sexual reproduction creates genetic variation.
An organism's size is only determined by its genes.	Growth is influenced by both genetic and environmental factors.

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Summary

• All life is made of cells with organelles that perform specific functions.

• Organisms reproduce sexually or asexually, using structures and behaviors for success.

• An organism's growth and energy processes are influenced by genetics and environment.

• Bacteria are prokaryotes; viruses are non-cellular and require a host to replicate.

Poll

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

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