Topic 1: Cells

Exceptions to Cell Theory & Differentiation

Mr Goodwin

Functions of Life

• All systems classified as “living” must be able to do the following on their own:– Reproduce + Pass on genes– Evolve + Respond + Adapt to their changing

environment– Metabolize nutrients + Excrete Waste– Grow + Develop over time– Maintain Homeostasis

The Cell Theory

• Once we know something is living, we also know it must follow the Cell Theory:– All living things are made of cells.– Cells are the most basic unit of life.– Existing cells come from pre-existing cells.

Exceptions to Cell Theory

1. Mitochondria & chloroplasts2. Viruses

Tissues and organisms not made of typical cells:3. Skeletal muscle4. Giant algae5. Aseptate fungi

Past paper question

Differentiation

• Cells become specialized for different functions by the process of differentiation

• Gives an advantage to multicellular organisms by allowing for a division of labor

Emergent properties• When units of biological material are put together, the

properties of the new material are not always additive, or equal to the sum of the properties of the components. Instead, at each level, new properties and rules emerge that cannot be predicted by observations and full knowledge of the lower levels. Such properties are called emergent properties (Novikoff, 1945).

• Life itself is an example of an emergent property. For instance, a single-celled bacterium is alive, but if you separate the macromolecules that combined to create the bacterium, these units are not alive. Based on our knowledge of macromolecules, we would not have been able to predict that they could combine to form a living organism, nor could we have predicted ALL of the characteristics of the resulting bacterium.