Biology and Cell Theory

What is Biology

● Bio: Life● Ology: Study

● In Grade 9 Science you studied Ecosystems & Human activity in your biology unit (the Large picture)

● This year (Grade 10) we will study cells, tissues & organs (the middle picture)

● If you take Grade 11 Biology you will focus on microbiology (the small picture)

What is Life?

● How can you tell something is living…..

● Talk to your classmates and brainstorm a list of characteristics that belong to ALL living things.

Characteristics of Living Things

All living things have common characteristics:

● Require food for energy● Break down food for energy● Limited lifespan● Respond to the environment● Grow● Reproduce● Produce waste ● Are made of CELL(S)

You are living. Where did you come from?

● Since you fulfill all the criteria for a living organism you are alive.

● If you are alive you are made of cells.

● Where did these cells come from?

Original Cell Theory

The original Cell Theory, developed mainly in the 1800s, claimed that:

1. All living things are composed of one or more cells.

2. Cells come from pre-existing cells.

3. Cells are the most basic unit of life.

Modern Cell Theory

The Modern Cell Theory has added several refinements:

● Cells contain DNA (deoxyribonucleic acid) which contains their genetic information and it is passed on each time a cell divides

● All cells are similar with regards to chemical composition and metabolic functions.

● All basic chemical and physiological functions are carried out inside the cell, such as digestion and locomotion.

● Cell activities are dependent upon sub-structures known as organelles.

Cell Size● Cells are small (1-100µm)

Cell Surface Area

Cells are small for good reason (transport):

a) Surface-to-volume ratio

b) Distance from surface to centre

Cell types

Until high school you learn about TWO cell types.

a) Animal b) Plant

These are important to distinguish.

Cell Sub-types

● Animal cells are not just of one type (as you have learned to date).

● There are variations that we call specialized cells

Different types of Animal cells

But there is more to categorizing cellsThere are varieties among animal cells:a) Prokaryotic

Ex: Bacteria cell; no nucleus (or other membrane bound organelles), circular DNA, ribosomes

b) Eukaryotic Ex: YOU are made of Eukaryotic cells; larger, nucleus, linear chromosomes and membrane bound organelles

Part of a cell - Organelles

● Cells are made up of smaller parts called organelles.

● These organelles perform the functions that the cell needs in order to live, much like your organs do for you.

Organelles and Cell Structures (Animal)

Organelles and Cell Structures (Plant)

Differences among Plant & Animal CellsPlant cells● Have cell walls● Have chloroplasts (in charge of photosynthesis)

Animal Cells● No cell walls● No chloroplasts (or photosynthesis)

Recap

● Cell Theory○ All living things are composed of one or more

cells○ Cells come from pre-existing cells○ Cells are the most basic unit of life

● Cells are made up of smaller parts known as organelles

● Plant and animal cells are different