(for ease, unless otherwise specified “organism”, “animal”, “plant” etc. refers to a living organism/animal/plant, etc.)

The Characteristics of Life:

Life Requires Materials and Energy:

• Biology: the study of life

• Characteristics shared by all living organisms:

  • Levels of organization

  • Ability to somehow get materials and energy

  • Ability to maintain an internal environment

  • Ability to respond to stimuli

  • Ability to reproduce and develop

  • Ability to adapt and evolve to changing conditions

• Everything is made up of atoms (living or non-living)

• Everything living (or formerly living) is made up of cells

  • Cells are the smallest unit of life

  • Anything in a cell or that makes up a cell isn’t living, but the cell itself is alive (or used to be alive)

• Most organisms on earth are single-celled organisms

  • This means the entire organism is made up of a single cell

  • Also called unicellular organisms

  • Bacteria and protists are unicellular organisms

• The rest of the organisms are multi-cellular organisms

  • This means the organism has more than one cell but they usually have way too many to count

  • Plants, fungi, and animals are multi-cellular organisms

  • There are different levels of organization within multicellular organisms:

    • A cell. A cell is the most basic level. Many cells usually come together to make…

    • Tissue. There are many different types of tissue. Tissues usually come together to make…

    • An organ. An organ has a specific job (or jobs, some organs have multiple functions) in the organism so there are many different organs for different jobs. Organs come together to make…

    • An organ system. An organ system has a broader job within the organism (for example the cardiovascular system which gets blood to the body, is made up of the heart, which pumps the blood, and blood vessels, which are the paths the blood goes through). Organ systems come together to make…

    • The organism. The organism is everything working together as a whole. It is the biggest level

• There are still more levels of organization larger than a single organism:

  • A species is a group of organisms that can breed with one another and therefore are similar to one another (EX: zebras are a species because they can all breed with one another. An elephant isn’t part of the zebra species because it can’t breed with a zebra successfully)

  • A population is all the members of a specific species in a specific area (EX: the zebra population in South Africa is made up of all the zebras in South Africa. If it’s not a zebra or it’s not in South Africa, it’s not in that population)

  • A community is made when populations in an area interact with one another (EX: The zebra population in South Africa, the human population in South Africa, and the tree population in South Africa all interact with each other so they form a community)

  • An ecosystem is made up of a community and the (non-living) physical environment around it (EX: the South African ecosystem is made up of the human, zebra, tree, etc. Community, and the soil, atmosphere, etc. Physical environment)

  • The biosphere is made up of all the ecosystems on the planet

Living Organisms Maintain an Internal Environment:

• In order to keep living, organisms need to keep everything relatively stable (EX: temperature, moisture level, acidity, etc.)

  • The balance is called homeostasis

• Some organisms can automatically adjust to maintain homeostasis

  • They have internal processes which can detect and fix an unbalance (EX: if you forget to eat, your liver will automatically release stored sugar to maintain blood sugar homeostasis)

  • Many of the organ systems in our bodies are used to maintain homeostasis

• Other organisms need to use their environment to fix an unbalance

  • EX: if a lizard is cold, it’ll find a warm spot to sit in until they warm up

Living Organisms Respond:

• Every organism either gets energy/nutrients or gets what it needs to make energy/nutrients from its surroundings

• Every organism gets cues (called stimuli) from its environment and responds in some way

  • This includes unicellular organisms

  • EX:

    • Unicellular organisms can beat microscopic hairs or snap whiplike tails (they can usually only do one) to move in response to light or chemicals

    • Monarch butterflies will migrate south in response to a change in season from summer to fall

    • Vultures will fly in response to smelling food

    • Leaves will turn in response to the sun’s movement

      • As shown by the examples, the response is usually a movement

• The right response at the right time is important to an organism’s survival

• All of the responses and daily activities an organism does is called the behavior of the organism

Living Organisms Reproduce and Develop:

• Every organism can reproduce

  • This means it can make another organism either identical to or similar to itself

• Unicellular organisms split to make 2 new organisms

• Multicellular organisms usually start reproduction when a sperm cell from one organism combines with an egg from another organism

  • This united cell divides many times and eventually results in an immature (as in young) organism which will grow and develop into a mature organism (as in fully grown)

• Genes determine everything about an organism from its species to its color to the proteins it makes

  • Different sets of genes determine different traits

• Genes are on long molecules called DNA (deoxyribonucleic acid)

• Differences in the genes lead to differences between different species as well as between different individuals within a species

  • Every variation found is a result of a mutation that was then passed on to new generations

    • Mutations are changes in the genetic sequence

    • The genetic variation they lead to is very important

    • Not all mutations are bad, some are good and some have no effect

      • EX of a bad mutation: the mutation that causes cystic fibrosis

      • EX of a good mutation: the mutation that increases bone density

      • EX of a mutation with no effect: the mutation that causes blue eyes

• Scientists learn a lot by studying DNA not only about an individual’s traits but also about a species’ evolutionary history

  • This is possible because genetic information is passed down through reproduction

  • This also shows how different species are related

• DNA is kind of like the blueprint for the organism

  • It contains all the information about the organization and metabolism of an organism

  • All cells in an organism have identical DNA but not all the genes are turned on in each cell

    • This means that while your skin cells have the genes for producing your eye color, the genes aren’t being expressed because they’re turned off so you don’t end up with blue skin to match your blue eyes

    • This allows cells to differentiate, form different parts of an organism and perform different jobs

    • Differentiation happens during the process of development

Living Organisms Have Adaptations:

• An adaption is a change that makes an organism more able to survive.

  • EX:

    • Hawks have strong eyesight which is an adaption that allows them to see prey on the ground from the sky

    • People who live at extreme elevations (over 13,000 ft or 4,000 m) in the Himalayas have an adaption that reduces the amount of hemoglobin in the blood. Hemoglobin levels usually increase with elevation as it helps with blood transport but hemoglobin also thickens the blood so the adaption prevents blood that is too thick.

Evolution: The Core Concept of Biology:

Natural Selection and Evolutionary Processes:

Organizing the Diversity of Life:

Science: A Way of Knowing:

Start with an Observation:

Develop a Hypothesis:

Make a Prediction and Perform Experiments:

Develop a Conclusion:

Scientific Theory:

An Example of a Controlled Study:

Publishing the Results:

Challenges Facing Science:

Biodiversity and Habitat Loss:

Emerging and Reemerging Diseases:

Climate Change: