Life Science Chapter 3 Lesson 2

Levels of Organization

• Multicellular organisms grow by making more cells, not larger cells.
• These cells work together to perform specific functions.
• Multicellular organisms have larger size and longer lifespan, due to specialization of cells.
• Specialization makes the organism more efficient in carrying out tasks.

Unicellular Organisms

• Unicellular organisms carry out all necessary life activities within a single cell.
• These cells interact with the environment and reproduce independently.
• Examples include bacteria.

Prokaryotes

• Prokaryotes are cells without a membrane-bound nucleus.
• These are smaller than eukaryotic cells.
• Bacteria are an example of prokaryotes.

Eukaryotes

• Eukaryotes are cells with a nucleus surrounded by a membrane.
• Examples include plants and animals.
• Eukaryotic cells have other specialized organelles that perform specific functions.

Cell Differentiation

• Cell differentiation is the process where cells become different cell types.
• Multicellular organisms develop from a single fertilized egg cell.
• Cells develop into different types like nerve cells, red blood cells, bone cells, or muscle cells.

Stem Cells

• Stem cells are unspecialized cells that can develop into many different cell types.
• Stem cells in embryos are more abundant than in adults.
• In adults, stem cells are important for repairing and replacing damaged cells.
• Stem cells are found in bone marrow and skeletal muscles in animals, and in meristems of plants.

Tissues

• Tissues are groups of similar cells working together to perform a task.
• Animals have four basic types of tissues.
• Nervous tissue carries messages between different parts of the body.
• Muscle tissue causes movement.

Connective Tissue

• Connective tissue provides support and connects other tissues together.
• It forms the protective outer layer of skin and lines internal body cavities.

Plant Tissues

• Plants have three basic types of tissues.: Dermal, Vascular and Ground
• Dermal tissue provides protection and helps reduce water loss.
• Vascular tissue transports water and nutrients.
• Ground tissue provides storage, support, and carries out photosynthesis.

Organs

• Organs are groups of different tissues that work together to perform a specific function.
• Examples in humans include the heart and stomach.
• In plants, organs include leaves, stems, and roots.

Organ Systems

• Organ systems are groups of different organs working together to complete a series of tasks.
• Examples include the digestive system, cardiovascular system, the shoot system of plants, and the root system.

Organism

• An organism is anything that can perform life processes, like humans or plants.
• Organisms are made up of cells and organized into higher levels like tissues, organs and organ systems.