LifeMrs. Boguslaw

7th Grade Science

Characteristics of Living Things

• Living things have cells

• Living things sense and respond to change

• Living things reproduce

• Living things have DNA

• Living things use energy

• Living things grow and develop

Living things have cells.

• cell: a membrane-covered structure that contains all of the materials necessary for life

• some organisms are one cell big, some are trillions of cells big

• cells can be specialized

Living things sense and respond to change.

• stimulus: anything that causes a reaction or change in an organism or any part of an organism

Living things sense and respond to change.

• homeostasis: the maintenance of a constant internal state in a changing environment

• chemical reactions keep organisms alive, and they need just the right conditions - homeostasis keeps these conditions stable and just right!

Living things sense and respond to change.

• What is a stimulus you encounter and what does your body do to maintain

homeostasis?

Living things reproduce.• sexual reproduction: reproduction in

which the sex cells from two parents unite, producing offspring that share traits from both parents

• asexual reproduction: reproduction that does not involve the union of sex cells and in which one parent produces offspring identical to itself

Living things have DNA.• DNA = deoxyribonucleic acid

• DNA controls the structure and function of cells

• When organisms reproduce, they pass copies of their DNA on to offspring

• heredity: the passing of genetic traits from parents to offspring

Living things use energy.

• Organisms use energy to carry out the activities of life, like making food, breaking down food, moving materials into and out of cells, and building cells.

• metabolism: the sum of all chemical processes that occur in an organism

Living things grow and develop.

• All living things, whether one cell or lots of cells, grow during periods of their lives

• Single-celled organisms: cell gets larger and divides

• Multicellular organisms: number of cells gets larger and organism gets bigger

• Living things might change as they grow and pass through different stages of life

The Necessities of Life

To live, almost every organism needs…

• water

• air

• a place to live

• food

• producer: an organism that can make its own food by using energy from its surroundings

• consumer: an organism that eats other organisms or organic matter

• decomposer: an organism that gets energy by breaking down the remains of dead organisms or animal wastes and consuming or absorbing the nutrients

Proteins

• protein: a molecule that is made up of amino acids and that is needed to build and repair body structures and regulate processes in the body

• proteins from food are broken down into amino acids, which are then linked together to form new proteins

Carbohydrates• carbohydrate: a class of energy-giving nutrients that

includes sugars, starches, and fiber; contains carbon, hydrogen, and oxygen

• source of energy and energy storage

• can be simple or complex

• simple: one (or just a few) sugar molecules

• complex: hundreds of sugar molecules, good for strong extra energy

Lipids• lipid: a type of biochemical that does not dissolve

in water; include fats (solid at room temperature), oils (liquid at room temperature), and steroids

• cannot mix with water

• can store energy or make up cell membranes

• phospholipids: a lipid that contains phosphorus and is a structural component in cell membranes

ATP

• ATP: adenosine triphosphate; main energy source for cell processes

• energy from carbohydrates and lipids must be transferred to ATP to provide fuel for cellular activities

Nucleic Acids• nucleic acid: a molecule made up of subunits

called nucleotides

• “recipe book” for proteins

• have all of the information for a cell to make proteins

• the order of the nucleotides determines the order of the amino acids that make a protein

• Includes DNA and RNA