1. All living things are made of cells. 2. The cell is the basic structural and functional unit of life. 3. All cells come from pre-existing cells.
Organisms-are individual forms of life that use energy to carry out activities. To be classified as living, something must be; ◦ Organized ◦ Grow and develop ◦ Respond to its environment; and ◦ Be able to reproduce. All organisms need energy, materials, and living space. All energy used by life on Earth comes from the Sun.
The cell is the smallest unit that can perform the basic activities of life. Multicellular organisms have specialized cells that, together, meet the basic needs. Unicellular organisms are made up of only one cell.- ex. Bacteria, some algae plants
Robert Hooke and Anton van Leeuwenhoek first described cells in the 1660s and 1670s. Microscopes were the new technology that led to their discoveries of many of the cells we have today.
Three types of microscopes are useful in studying cells. ◦ Light microscopes can magnify living cells. ◦ Scanning electron microscopes and transmission electron microscopes can magnify smaller objects, but preparation of living specimens kills them. Transmission Electron - Scanning Electron-
In the 1850s people knew for sure that cells come from other cells. This fact is part of the cell theory: 1. All living things are made of one or more cells. 2. Cells carry out the functions needed to support life. 3. Cells come only from other living things.
A theory is an explanation of what is observed, and must be supported by evidence. Louis Pasteur used the cell theory as a foundation for his studies. He found that: ◦ Bacteria causes food spoilage, sour milk, and many diseases. ◦ Living things do not arise by spontaneous generations.
All cells have cell membranes as a protective covering. They all contain cytoplasm, a thick fluid where most of the work of the cell is done. Most cells also have genetic material, called DNA (Deoxyribonucleic Acid). ◦ In prokaryotic cells, DNA is in the cytoplasm. ◦ In eukaryotic cells, DNA is separated from the rest of the cytoplasm in a nucleus.
Eukaryotic cells are much larger than prokaryotic cells. They have many complex structures, including organelles. Prokaryotic cells lack a nucleus and other organelles, with DNA that is not organized into chromosomes. Organelles called chloroplasts use energy from sunlight to make sugar. Cells have mitochondria to make energy available to the organism. The endoplasmic reticulum, ribosomes, and Golgi apparatus process and transport materials. Other organelles such as vacuoles and lysosomes store and recycle water and waste.
Organisms can be classified by their cell type. ◦ Most organisms on Earth are unicellular. They can be in one of three domains. Archaea- are prokaryotes that mostly live in extreme environments. Bacteria- are prokaryotes that share some similarities with archaea, but grow virtually everywhere on Earth. Eukarya-are eukaryotes, which include multicellular organisms (plants, animals, fungi and some protists) and unicellular organisms (some protists).
All multicellular organisms begin life as a single fertilized egg cell. As cells divide, they specialize to perform specific jobs. The more specialization there is, the more complex the organism is.
Organisms have different degrees of organization. For example, sponges have specialized cells, but are not strictly organized. ◦ Similar cells group together to form tissues. ◦ Tissues act together to form organs. ◦ Organs and tissues act together in organ systems.
Scientists use models to make complicated structures or processes easier to understand. ◦ Some examples of models include mathematical or chemical equations, diagrams, process models, or physical models. DNA Model- created by Watson and Crick