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IB Biology refers to the International Baccalaureate (IB) group 4 experimental science Biology.

The following is (or will hopefully eventually be) an explanation of the entire IB Biology Syllabus: For first examinations in 2003.

The Syllabus provided by the International Baccalaureate Organization (IBO) consists of the titles displayed in bold. The explanations written in plain text below these titles have been added as supplementation and/or when further clarification is required. Basically, it takes away the need to research the "answers" to the syllabus and gives everyone a study-guide which can be accessed from anywhere, whenever needed.

Contents 1 Cell Theory 1.1 The theory that living organisms are composed of cells. 1.2 Note that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat. 1.3 All cells are formed from other cells. 1.4 Three advantages of using light microscopes. 1.5 The advantages of using electron microscopes. 1.6 Define organelle. 1.7 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. 1.8 Calculate linear magnification of drawings. 1.9 The importance of the surface area to volume ratio as a factor limiting cell size. 1.10 State that unicellular organisms carry out all the functions of life. 1.11 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. 1.12 Define tissue, organ and organ system. 2 Prokaryotic Cells 2.1 Draw a generalized prokaryotic cell as seen in electron micrographs. 2.2 State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA. 2.3 State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation. 3 Eukaryotic Cells 3.1 Draw a diagram to show the ultrastructure of a generalized animal cell as seen in electron micrographs. 3.2 State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondrion and nucleus. 3.3 Compare prokaryotic and eukaryotic cells. 3.4 Describe three differences between plant and animal cells. 3.5 State the composition and function of the plant cell wall. 4 Membranes 4.1 Draw a diagram to show the fluid mosaic model of a biological membrane. 4.2 Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes. 5 Topic 4: Ecology and Evolution 6 Option D - Evolution 7 Option G - Ecology and Conservation

Cell Theory

The theory that living organisms are composed of cells.

Cells are the structural and functional units of all living organisms ("the building blocks of life"). The Cell Theory states:

1. All organisms are composed of one or more cells.
2. All cells come from pre-existing cells.
3. All vital functions of an organism occur within cells.
4. Cells are the most basic unit of life
5. Cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

Exceptions: Skeletal muscle and some fungal hyphae are not divided into cells but have a multinucleate cytoplasm. Extracellular material (material outside the cell membrane), such as teeth, forms a significant part of the body. Some biologists consider unicellular organisms to be acellular.

Note that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat.

All cells are formed from other cells.

Three advantages of using light microscopes.

Light microscopes:

1. Display colour instead of monochrome (black and white) images.
2. Provide a large field of view.
3. Facilitate preparation of sample material.
4. Allow for the examination of living material and the observation of movement.

The advantages of using electron microscopes.

Electron microscropes:

• Provide images of higher resolution and magnification than light microscopes.

• Resolution refers to the ability to distinguish two objects as seperate entities.
• Magnification refers to the ability to increase the size of a viewed objects.

Scanning Electron Microscopes (SEM) provide images of the specimen's surface while Transmission Electron Microscopes (TEM) provide images of a sample's interior. The resolution of an SEM is approximately half that of a TEM.

Define organelle.

An organelle is a discrete structure within a cell, and has a specific function.

Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units.

1. Molecules (1 nm)
2. Cell membrane thickness (10 nm)
3. Viruses (100 nm)
4. Bacteria (1 µm)
5. Organelles (<10 µm)
6. Most cells (<100 µm)

Note: Cells are three-dimensional. So is everything else described here?

Calculate linear magnification of drawings.

Drawings should show cells and cell ultrastructure.

Include:

A scale bar: |------| = 1 µm

Magnification: ×250

To calculate magnification:

Magnification = Measured Size of Diagram ÷ Actual Size of Object

The importance of the surface area to volume ratio as a factor limiting cell size.

The rate of metabolism of a cell is a function of its mass:volume ratio.

The rate of exchange of materials (nutrients/waste) and energy (heat) is a function of its surface area.

Thus: As a cell grows in size (volume), the distance increases between the cytoplasm at the center of the cell and the cell membrane. The rate of chemical exchange with the surrounding environment may hence become too low to maintain the cell.

Volume of a cell determines requirements while surface area determines supply.

State that unicellular organisms carry out all the functions of life.

Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.

During the early development stages of multicellular organisms, cells undergo differentiation, becoming specialized in structure and function. These cells are then organized into tissues and organs. Cells of multicellular eukaryotes express only a small fraction of their genes, allowing them to perform highly specialized functions. Cells, such as those of muscle or nervous tissue, express only a tiny fraction of their genes.

Define tissue, organ and organ system.

• Tissue: An integrated group of cells that share stucture and function.
• Organ: A combination of two or more tissues which function as an integrated unit, performing one or more specific functions in an orgranism.
• Organ system: A group of organs that specialize in a certain function together.

Prokaryotic Cells

Draw a generalized prokaryotic cell as seen in electron micrographs.

State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA.

1. Cell Wall: Maintains the cell's shape
2. Plasma Membrane: Regulates the flow of materials (nutrients, waste, oxygen, etc.) into and out of the cell
3. Mesosome: Increases the cell's surface area to volume ratio
4. Cytoplasm: Holds and suspends the cell's specialized organelles
5. Ribosome: Main site for protein synthesis
6. Naked DNA: Contains the cell's genes

State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation.

Eukaryotic Cells

Draw a diagram to show the ultrastructure of a generalized animal cell as seen in electron micrographs.

State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondrion and nucleus.

1. Ribosomes: Main site of protein synthesis
2. Rough endoplasmic reticulum (rER): Packages the proteins synthesized in the ribosomes
3. Lysosome: Digests macromolecules
4. Golgi apparatus: Modifies, stores and routes products of the endoplasmic reticulum
5. Mitochondrion: Serves as the site of cellular respiration
6. Nucleus: Contains a cell's chromosomes

Compare prokaryotic and eukaryotic cells.

Prokaryotic cells vs. Eukaryotic cells

• Contain naked DNA vs. DNA associated with protein
• DNA in cytoplasm vs. DNA enclosed in a nuclear envelope
• No mitochondria vs. mitochondria
• 70S vs. 80S ribosomes

Describe three differences between plant and animal cells.

Only plant cells contain:

• Cell walls
• Chloroplasts
• Large central vacuoles and tonoplast
• Plasmodestmata
• Starch granules for storage of Carbohydrate

Only animal cells contain:

• Lysosomes
• Centrioles
• Flagella
• Glycogen for storage of Carbohydrate

State the composition and function of the plant cell wall.

The main component of plant cell walls is cellulose. Cellulose molecules are arranged in bundles called microfibrils. These give the cell wall great tensile strength and allow high pressures to develop inside the cell.

Membranes

Draw a diagram to show the fluid mosaic model of a biological membrane.

Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.

Hydrophilic molecules are attracted to water. Hydrophobic molecules are not attracted to water, but to themselves. Phosopholipid molecules are both hydrophobic and hydrophilic. The attraction between the hydrophobic tails in the center and the hydrophilic head being attracted to the surrounding water makes the membrane very stable.

Topic 4: Ecology and Evolution

Option D - Evolution

IB Biology Option D - Evolution

Option G - Ecology and Conservation

IB Biology Option G - Ecology and Conservation