characteristics of living and non-living things

Is a seed alive? Some children will say it it living because it will sprout and grow one day. Others will say it is non-living because it does not move. It is true that movement is a common characteristic of living things. However, many non-living things (e.g., cars, wind) also move. To identify living things, scientists look for evidence of the following characteristics:

• Movement: Does it (or parts of it) move in some way?
• Reproduction: Does it produce offspring?
• Organization: Does it have parts (e.g., cells, organs) that perform specific functions?
• Growth and development: Does it grow? Does it have a life cycle?
• Energy: Does it use energy? Does it produce waste (e.g., carbon dioxide)?
• Response: Does it respond to the environment?

Some living things are difficult to classify because they are dormant (like the seed) or dead.  Unlike dormant or deceased living things, non-living things will not exhibit the characteristics of living things in either the past or future.

Cell Theory

How many cells do you think your body is made of? Watch the video below to find out the answer and to learn about the development of cell theory

“Cell Theory” by Khan Academy

To sum up, cell theory has three main ideas:

• All living things are made of one or more cells.
• Cells are the basic unit of structure and function of living things.
• Cells come from pre-existing cells. Cells pass their genetic material (e.g., DNA) to the next generation of cells.

The theory has been refined as we have learned more about cell processes such as cellular respiration, protein synthesis, mitosis and meiosis.

plant and animal cells

All cells have specific parts (organelles) that work together to keep the cell alive.  The cells of all living things share many of the same structures. The following common structures are responsible for the same functions regardless of type of living thing.

• Cell membrane: Allows some materials to enter the cell and blocks others
• Nucleus: Houses the hereditary material (DNA) which directs cell processes
• Mitochondria: Transforms food (glucose) into usable energy for cell processes
• Ribosomes: Produces proteins
• Endoplasmic reticulum (ER): Transports of proteins, produces fatty compounds (lipids)
• Golgi apparatus: Processes and packages materials, transports lipids
• Vacuoles: Stores materials

Unlike animal cells, plant cells have a cell wall and chloroplasts. The cell wall gives plant cells additional support and protection. Chloroplasts allow plant cells to produce their own food (glucose) through photosynthesis. Plant cells also have a single large vacuole which stores water and other materials.

Unlike plant cells, animal cells have centrioles which assist with cell division. Animal cells also have many small vacuoles for storing materials.

Watch the video below discussing additional similarities and differences between animal and plant cells.

“Plant Vs. Animal Cells” by the Amoeba Sisters

Classification of living things

Scientists estimate that less than 15% of the living things on Earth have been identified and classified. The modern classification system has been revised many times. It currently includes eight levels. As you move down the levels, each level contains smaller and smaller groupings of living things until you reach the species level, which represent a single living thing.

• Domain (largest groups of living things)
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species (single organism)

The scientific name of a single living thing is a combination of its genus and species. For example, the scientific name of a lion is Panthera leo. Watch the video below to learn about the full classification of the lion.

“Classification of Living Things” by Mark Drollinger is licensed under CC BY NC ND 4.0.

Animal structures and functions

Humans have many of the same organ systems as other animals, especially other vertebrates and mammals. These systems are composed of organs and tissues that work together to accomplish a specific function. Below is a list of common systems and their functions:

• Nervous: Controls all other systems, receives and processes information about the environment
• Skeletal: Protects internal organs (e.g., brain, heart, lungs) and allows for movement
• Muscular: Moves the bones and supports breathing, blood flow, and digestion
• Circulatory: Moves oxygen-rich blood throughout the body
• Respiration: Pulls oxygen from the air during inhalation, releases carbon dioxide into the air during exhalation
• Digestion: Breaks down and absorbs nutrients from food, processes waste from food
• Excretory: Filters the blood and removes extra water and wastes
• Reproduction: Produces eggs (female) and sperm (male), and supports and nourishes the developing fetus (female)

Watch the video below to learn more about the structure and function of human body systems.

“Human Body Systems” by the Amoeba Sisters

infectious agents and human diseases

Humans are susceptible to infection from many viruses, bacteria, fungi, and parasites. Some of these infections can result in disability and death while others are a mere temporary inconvenience. Good hygiene practices and vaccines have greatly reduced the rates of many common infections. Some infections are treatable with medications. For example, bacterial infections can be treated with antibiotics. However, antibiotics cannot be used to treat viral, fungal or parasitic infections. The table below provides examples of different infectious agents and the infections they can cause.

Table 1. Various infectious agents

heredity

Children (offspring) often resemble their parents in many ways. Heredity is the reason why this is so.  Some characteristics (inherited traits) are passed from parents to offspring through genetic material (e.g., DNA).  These traits can be physical or behavioral. Offspring receive half of their genetic material from one parent and half from the other parent. Below is a list of some common inherited traits in humans:

• Dimples
• Freckles
• Left/right handedness
• Red/green colorblindness

In contrast, some traits are changed through personal experiences and formal/informal learning throughout our lives (acquired traits). Below is a list of some common acquired traits in humans:

• Language
• Reading
• Tattoos
• Calluses on hands

Watch this video to learn how many traits in people are influenced by both genetic and environmental factors. Then take the Nature or Nurture quiz.

natural selection and evolution

Biological evolution over 3.8 billion years is responsible for the great diversity of life on Earth. Evolution includes both the changes in the genes and related traits within a single group (population) of living things (species), and the development of entirely new species from existing species. Watch this video describing the adaptations of a species of lizard in cities in Puerto Rico.

Natural selection is one of the processes that can result in evolution. Explore the simulation below to find out a little about how natural selection works.

Natural selection involves five basic steps. The mnemonic device, VISTA, can be used to remember these steps (American Museum of Natural History, n.d.).

1. Variation: Members of a species are unique individuals that vary in their traits. Some of these unique traits come from mutations in genes.
2. Inheritance: Parents pass on some of their unique traits to their offspring through their DNA.
3. Selection: Some individuals survive to reproduce due to favorable traits that allow them to escape predation, find more food, survive changes in the environment, etc.
4. Time: Over generations, the traits that help individuals to survive and reproduce in greater numbers become more common in a population.
5. Adaptation: The population of organisms becomes better adapted to the unique environmental conditions than before.

Read about common misconceptions about natural selection and evolution here. For example, some students may think that natural selection involves organisms actively trying to adapt. This is not factual.

interdependence of living things and the environment

Ecosystems contain all of the living and non-living things in a particular geographic area. The organisms in an ecosystem depend on each other and the environmental for survival. Organisms interact through feeding relationships, competition for limited resources, and symbiotic relationships. Changes in ecosystems (e.g., pollution, habitat destruction) can cause a chain reaction which affects many different species.

Food chains and food webs are visual representations of the feeding relationships between producers and consumers in ecosystems. Food webs are often composed of multiple overlapping food chains. The arrows in food chains show the energy flow from one organism to another (e.g., producer->consumer). Below are examples of food chains.

• Seaweed (primary producer)->abalone (primary consumer)->sea star (secondary consumer)->sea gull (tertiary consumer)
• Grass (primary producer)->deer (primary consumer)->bear (secondary consumer)

Watch the video below to learn about food chains in the Everglades ecosystem.

“The Food Chain” by Odyssey Earth

Now try building your own food chains using this interactive.

Platte River prairie ecosystem: Food chain interactive

plant structures and functions

Just like the organs of animals, plant parts work together to keep the plant alive. Check out the parts of plants and their functions using this interactive plant. Many of the functions are related to the processes of photosynthesis, transpiration, and reproduction. The table below summarizes these three processes and where they occur in flowering plants.

Table 2. Plant processes

Some plants can also reproduce asexually, meaning that that they reproduce without exchanging pollen or spores (in the case of ferns or mosses). Offspring simply grow from a part of the parent plant and have the same genetic information as the parent. Many plants that we eat can reproduce asexually such as strawberry, white potato, sweet potato, garlic and onion. This process is called vegetative propagation.

Plant responses to stimuli

Plants are alive! Therefore, they do respond to their environment. Plants respond to light, heat, gravity, water,  movement of the sun, and even touch. These responses are called tropisms. In some cases, the plant will move towards the stimuli, and in other cases, the plant will move away from the stimuli. Watch the following video showing how young sunflowers track the sun.

“How Young Sunflowers Track the Sun’s Movements” by the Australian Academy of Science

life cycles of plants and animals

Plants and animals, like all living things, have a life cycle. Young plants and animals grow and develop, reproduce as adults, and eventually die. Life cycles of common Florida plants and animals are summarized below. Some young insects look like small versions of the adults (incomplete metamorphosis) while others look very different from the adult stage and go through many changes as they develop (complete metamorphosis).  Some amphibians (e.g., frogs, toads, salamanders) also go through a process of metamorphosis.

Longleaf Pine Tree

• Seed
• Seedling
• Grass stage
• Bottlebrush stage
• Sapling stage
• Adult (reproduces with cones)

Purple Passionflower (host plant for Zebra Longwing)

• Seed
• Seedling
• Adult (reproduces with flowers)

Zebra Longwing (undergoes complete metamorphosis)

• Egg
• Larvae (caterpillar)
• Pupae (crysallis)
• Adult (has wings)

American Cockroach (undergoes incomplete metamorphosis)

• Egg
• Nymph
• Adult (has wings)

Squirrel Treefrog (undergoes metamorphosis)

• Egg
• Larvae (tadpole with gills and a tale)
• Juvenile (has developing lungs and legs)
• Adult (has lungs and legs)

Explore the interactive lesson below to learn more about life cycle of another Florida butterfly, the painted lady butterfly. You might be surprised at what you didn’t know.

Butterfly life cycle interactive lesson

FTCE K-6 Life Science Outcomes

Below are the outcomes related to the Life Science competency for the FTCE K-6 exam:

1. Identify and compare the characteristics of living and nonliving things.
2. Analyze the cell theory as it relates to the functional and structural hierarchy of all living things.
3. Identify and compare the structures and functions of plant and animal cells.
4. Classify living things into major groups (i.e., Linnaean system) and compare according to characteristics (e.g., physical features, behaviors, development).
5. Compare and contrast the structures, functions, and interactions of human and other animal organ systems (e.g., respiration, reproduction, digestion).
6. Distinguish among infectious agents (e.g., viruses, bacteria, fungi, parasites), their transmission, and their effects on the human body.
7. Identify and analyze the processes of heredity and natural selection and the scientific theory of evolution.
8. Analyze the interdependence of living things with each other and with their environment (e.g., food webs, ecosystems, pollution).
9. Identify and analyze plant structures and the processes of photosynthesis, transpiration, and reproduction (i.e., sexual, asexual).
10. Predict the responses of plants to various stimuli (e.g., heat, light, gravity).
11. Identify and compare the life cycles and predictable ways plants and animals change as they grow, develop, and age.

References

How does natural selection work? (n.d.) American Museum of Natural History. Retrieved August 15, 2023 from https://www.amnh.org/exhibitions/darwin/evolution-today/natural-selection-vista