Biology and Cell Theory

SNC2P

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)

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 celltypes.

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)

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