Unit 2

  • Created by: Grace
  • Created on: 24-03-13 12:03


Cells are the basic structural and fuctional of life therefore it is capable of the seven characteristics of life.

Tissues: Group of the same cells working together. For example; bone

Organs: Groups tissues working together. For example; brain

Systems: Groups of organs working together. For example; digestive

Orgamisms: Groups of systems working together.

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Magnification: A measure of how many times bigger the image is, compared to the object

Resolution (resoving power): A measure of their ability to distiguish between two separate points

Dfferences between types of EM:

Trasmission: 2D images. Scanning: 3D images

Transmission: Speciman has to be dead (in a vacuum). Scanning: Alive (coated in metal)

Transmission: Photograph in black and white. Scanning: Cells, tissues and orgamisms are imaged. 

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Comparing Optical and EM Microscopes

Optical                                                                                  Electron

- specimencan be living                                            - specimen must be dead 

- uses light waves                                                     - uses a beam of electrons

- 250nm resolution                                                    - 0.1nm resolution

- up to 1500x magnification                                       - up to 2x10x magnification

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Eukaryote Cells 1

(after the nucleus) - cells of animal, plants, fungi and protistics. Consiting of one or more cells that contain DNA in a membrane bound nucleus, separate from the cytoplasm.



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Eukaryote Cells 2

Plant Cells - share common features of animal cells. Gain energy from sunlight; chloroplasts use this to convert into something useful


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Eukaryote Cells 3

Choroplasts - use carbon dioxide, water and light enery. Present in all green plants. surronded by a double membrane - filled with liquid called stroma and contains stacks of thylakoid membranes called grana - this is the site of photosynthesis


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Eukaryote Cells 4


Permanent vacuoles are only in plant cells. animal cells contain vacuoles but are not that common. Important in keeping the cells tirgid (firm).

Cell Wall

gives support and structure, made from polyscarraride cellulose and can act as a carbohydrate by varying the amount of cellulose it holds.

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Diagram of a Eukaryote Cell


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Prokaryote Cells

before the nucleus - including bacterical cells

usually single-celled - whose DNA is suspended freely in the cytoplasm. divided into two groups: Bacteria and Achaea.

Flagella and Pili

Flagella are long helical shape tubes extending out of the cells wall which rotate to provide loemotion. These are powered by protein motors and can propel bacteria at a rate of more than 50 lengths a second. Pili are hollow protein structures used during bacterial conjugation


These are small continuous loops of DNA and are replicated independently of a bacterium's gonophore and may confer an advantage such as antibiotic resistance.

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Diagram of a Prokaryote Cell


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Endoplasmic Reticulum (ER)

ER is a complex mass of membranes which run though entire cells and it is an extension of nuclear membranes. ER has complex structures with: cisternae (membrane lined tubules/channels).

RER (rough) - studed with ribosomes.

The role of RER is to allow ribosomesto synthesize and modify proteins. To transport and deliver proteins around and out of the cell.

SER (smooth) - no ribosomes

The role of SER is to synthesize steriods and lipids and to store carbohydrates

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Diagram of the Golgi


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Information on the Golgi

- complext collection of stacked membranes

- very prominate in the cells that have secretory functions

- cis and trans surfaces

- activity starts from the cis face (reciving) and moves towards trans face (shipping)


-  carbohydrate is added to proteins to form glycoproteins

- formation of lysosomes

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Movement of Proteins in a membrane


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Explanation of 'Movement of Proteins in a membrane

1. Nucleus contains DNA. This codes for a protein and then DNA is converted to mRNA

2. mRNA leaves nucleus and travels to ribosomes on the RER

3. mRNA is translated and a polypeptide is synthesized

4. Polypeptide is sent to golgi body for modification

5. A carbohydrate is usually added

6. Glycoprotein is packaged and pinched off into a vesicle

7. Vesicle moves to the plasma membrane and the protein is released by exocytosis

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The Cell Cycle


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The Cell Cycle Explained

G1 (first growth stage) - most of the time is spent in here. organelles are replicated for example the ER. A cells that is not destined to divide stays in G1 but if a cells is suppose to divide enters the S phase

S (synthesis phase) - this is where the DNA is replicated so the volume doubles. Each chromosome ends up with 2 chromatids joined at the centre

G2 (second growth stage) - period between s and mitiosis, invloves more growth and the centrioles replicate

Chromosomes - single, very long strand of DNA and is supported and neatly packaged by proteins.

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How to prepare a Root Tip to observe Mitosis

1.     Cut a root tip from a growing root

2.     Place in on a watch glass and add a few drops of HCl to the tip

3.     Add a couple of drops of acetic orcein

4.     Warm the watch glass

5.     Place the root tip on a microscope slide and use a needle to break it open and spread the cells

6.     Add a few more drops of stain and place a cover slip over the root tip and gently press down on it

7.     Warm the slide to intensify the stain then place under a microscope to observe

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A special form of cell division. The two functions are; 1) to form haploid cells with half the chromosome number, 2) to re-arrange the chromosome with a novel combination of genes


-       Separation of chromatids

-       Chiosma formation and exchange between chromatids

-       Formation of bivalents

-       Paring of homologous chromosomes

-       Production of haploid cells

Genetic variation is achieved by; independent assortment, crossing over or random fertilisation

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Structure of a Typical Flower


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Fertilisation in Plants

Fertilisation - the fusing of the gametes

Plants: male - pollen grains in the anthers. Female - ovule in the overies


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Fertilisation in Plants 2

Ovule - seven nuclei present six are hapliod and one is diploid


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Steps of the Fertilisation Process of Plants 1

1.     The pollen grain sticks on the stigma surface.

2.     The pollen grain absorbs water, swells and splits open.

3.     The stigma secretes a sucrose solution.

4.     The sucrose solution stimulates the growth of the pollen tube.

5.     The ovary releases chemicals to encourage the growth of the tube in the right direction. The tube nucleus at the tip organises the growth.

6.     As the tube grows it digests its way through the style and ovary wall tissue.

7.     The pollen tube grows through the micropyle.

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Steps of the Fertilisation Process in Plant 2

8. As it penetrates the embryosac the tube tip and tube nucleus disintegrate.

9. The other five nuclei in the embryo disintegrate.

10. The generative nucleus divides by mitosis to form male gamete nuclei.

11. The two male gametes are released.

12. In a double fertilisation, one male gamete fuses with the ovum to form a diploid zygote nucleus, while the other male gamete nucleus fuses with the two polar nuclei to form the triploid primary endosperm nucleus.

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Sperm Diagram


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Egg Diagram


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Differences in the Sperm and Ova

Sperm do not need a food store but the ova does

Sperm are motile, whereas eggs are fixed

Many sperm are produced but only a few ova are produced

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Fertilisation is the process by which a male and female gamete nuclei fuse together to produce a dipolid zygote


eggs are liberated in water and the female lays a large number of eggs then the male pours its sperm over the same region of water. Fertilisation takes place outside (eg fish)


takes place inside the body (occurs in animals who have a well developed reproductive system). Fewer eggs than external because of the protection from its mother.

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The Ovum

Large oval cells which varies from 117-142

inner layer called the vitelline membrane

outer think transparent membrane called the zona pellucida

corona radiata; 2/3 layers of cells which sorround the zona pellucida

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The Sperm

freshly ejaculated sperm (300-500 million) are unable to fertilise ova. They must first undergo a series of changes known as the capacitation. the sperm cell membrane may be altered by changing its lipid compostition by lowing cholesterol.

Why do Sperm need energy?

Fructose for respiration to provide energy for the sperm to swim to the egg and is the energy source in the semen. It is respired aerobicly to release energy in the form of ATP, the energy is used in the tail to swim to the ovum.

Capacitation appears to prepare the sperm for the acrosome reaction, only capacitated sperm can pass though the corona cells of the ovum and undergo the acrosome reaction.

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The Acrosome Reaction

The acrosome is a bag of enzymes located on the top of the head of the sperm.

The acrosome of the sperm releasses proteolyic (protein digesting) enzymes.

The enzymes digest a path through the outer layers of the ovum.

The egg membrane forms microvili which fuse with the sperm membrane and draw it to the egg.

Prior to fertilisation, the egg is in a dorment state, arrested in the metaphase of the second meiotic division.

Upon binding with the sperm, the egg rapidly undergoes a number of metabolic and physical changes and completes meiosis II

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The Cortical Reaction

The fusion of egg & sperm membranes stimulates a series of changes in the egg's cortex known as a cortical reaction.

Chemical reactions changes the egg's cortical granules (forms a thick barrier).

Granules fuse with the plasma membrane releasing enzymes separating the vitelline layer from the plasma membrane.

Swelling 'lifts' the vitelline membrane forming the fertilisation membrane.

This prevents penetration by other sperm.

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Stem Cells

Stem Cells are undifferentiated from which all of the body's maturem differentiated cells are made.

Stem Cells give rise to brain, nerve, heart cells ect.

The zygote undergoes 3 mitotic divisions resulting in 8 identical cells.

These cells are said to be totipotent because they are each capable of developing into all of the different types of cells which make up the orgamism. 5 days after fertilisation a hollow ball called a blastocyst us formed.

The placenta forms from the outer layer. The embryo is formed from the inner mass, which is made up of about 50 cells. Inner mass cells are called pluripotent embryonic stem cells. Each cells of the inner mass can potentially develop into all other cell types. Most differentiate into a specific cell type. In the adult some retain the capacity to differentiate into one of many types of cells. They are multipotent.

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Stem Cell Meanings


A totipotent stem cell can produce all cell types, including all specialised cell types and extraembryonic cellls


A pluripotent stem cell can produce all specialised cell types by not extraembryonic cellls

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Types of Stem Cells

Embryonic (pluripotent) - these are capable of developing into all the cell types of the body but not embryonic cells (eg, placenta)

Adult stem cells - less versatile and more difficult to identify, isolate and purify.

Embryo from IVF clinic or nuclear transfer-->blastocyst-->extracted stem cells-->stem cell line

                                                                              cultured pluripotent stem cells

                                                               New Tissue -- pancreas, bone, brain, kidney (ect)

Researchers extract stem cells from a 5-7 day old blastocyst. Stem cells can divide in culture to form more of their own kind, thereby creating a stem cell line. The research aims to induce these cells to generate healthy tissue needed by patients.

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Stem Cells from IVF


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Human Therapeutic Cloning (SCNT)


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Adult Stem Cells

In adults, some stem cells retain the capacity to differenticate into one of many types of cells. They are said to be multipotent.

These cells are present in adults as:

1. Neural Stem Cells - can develop into various types of nerve cells

2. White Blood Stem Cells - white blood cells (all types), red blood cells, platelets (bone marrow)

Stem cells have the potential to replace cell tussue that has been damaged or distroyed by severe illnesses. They can replicate themselves over and over for a very long time. Understanding stem cells can be developed to assist the search for cures. Can be used to research:

How genes control human development, how genes trigger the onset of organ formations, how cancer cells develop, how certain birth deficts develop

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Ethics of using Stem Cells

ESCR - Embryonic Stem Cell Research

For ESCR: Fulfills the ethical obligation to alleviate human suffering, therapeutic cloning produces cells in a petri dish - not a pregnancy. Since excess IVF embryos will be discarded, isn't it better that they are used in valuable research?

Against ESCR: Stem cells are taken from a human blastoocyst, which is then distroyed. This amounts to murder. There is a risk of commercial exploitation of the human participants in ESCR.

Key Ethical Issues: The blastocyst used in stem cell research is microscopically small and has no nervous system. Does this count as a 'person' who has a right to life? What do various religions say about when personhood begins? Does science have a view on this? In a society where citizens hold diverse religious views, how can we democratically make humane public policy?

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Polygenic Inheritence 1

- Characteristics which fall into distinct categories are said to be discontinuous variation eg eye colour.

- Single-gene inheritance is where characteristics are controlled by the alleles of only one gene.

- Characteristics which show a range of differences from one extreme to anothe are said to show continuous variation.      

- Polygenic inheritance is when characteristics are controlled by the alleles of more than one gene. Characteristic bell shape curve for continuous variation - normally distributed.

- Polygenic phenotypes exhibit continuous variation, since each different gene permutation results in just a small phenotypic change.

- Traits all result from the interaction of the genes with envrionmental factors

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Polygenic Inheritence 2

Types of inheritance                        Single-Gene                      Polygenic

Number of genes                                    One                               Many

Number of phenotypes                           One                              Several

Type of Variation                               Discontinous                   Continuous


Single-gene inheritance - blood group, tounge rolling, right/left handed

Polygenic inheritance - height, skin colour, eye colour

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The Plant Stem

The plant stem is a plant organ and has many functions. Some listed below;  

-   to hold the leaves in the best postition for photosynthesis

-   to support the flowers - to maximise pollination

-   ability to bend and not break when exposed to the elements

-   strong to remain upright      

 -   transport of substances for example water, surcrose

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Low Power Tissue Map - Plant Stem


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Dicot Stem (plant stem)


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Uses of Plants

Some uses:






Cotton -  outgrowthsof epidermal cells of Gossypiums. Tensile strength is the ability to resist being broken when stretched. It represents the maximum load/force which can be applied before breaking.


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- Soaking in water for about a week is called retting. Retting plant material smells strongly

- Removing the leaves and flowers reduces the smell as they make a slimy mass when rotting

- After soaking for a week all the soft tissue will wash away in running water

- Wash the stems to remove the softened tissue and then dry the remaining fibres

- The outside cuticle and epidermal layer will rub away and the central pith will be left when you peel away the fibres

- These fibres are made up of vascular tissue, they contain both the xylem vessels and sclerenchyma fibres

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Uses of Wood

Redwoods - (Sequia) are prized for wood. They produce substances which inhibit the growth of bacteria and fungi

Spruce Wood - important in the music instrument industry, for example violins

Resin - (in the trunks). This is a combination of turpentine and resin, which are used in the ship making industry

Nylon and Rayon are processed from wood fibres

Paper - conifers produce over 75% of world's timber. Wood pulp is used to make paper

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Other Uses of Plants

Lavender - (Lavandula). This was used by the Romans to scent and disinfect their baths

Sassafras - Used in toothpaste, gum, tea and beer

Camellia - used to make tea

Para rubber tree - provides latex for rubber

Candelilla - source of candle wax

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Foxgloves - produces digitalis - used to treat heart disease

Taxol - bark of the pacific yew tree - one of the most promising anti-cancer drugs

Rosy Periwinkle - from Madagascar - treats two cancers - juvenile leukemia/Hodgkins disease

Salix - willow - used to treat headaches and arthritis - an anti-inflammatory

Cinchona - fever bark tree - source of quinine - used to treat malaria

Dioscorea - from the yam - used in the production of sex hormones and oral contraception

Plants as food

Maize, flour, fruit, vegetables, nuts, rice, wheat

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Anti-bacterial Properties of Plants

Which is the most effective herb out of mint, garlic, sage, rosemary at killing bacteria.

Preparing the herb and the method:

3g of each herb. Grid the herb then add 10cm cubic of alcohol (disolves the antibacterial agent). We grind the herb to release the agent in alcohol because the cell wall is broken. The fluid in the dish is transfered to a beaker and then a drop is placed on a sheet of stirile filter paper. This is left to dry by a roaring flame once dried it is transfered to a petri dish with a thin layer of e-coli on. There are two controls of which are ethanol and distilled water. This is left for 24 hours and then the clear zone is measured by using two diameters. The larger the clear zone diameter, the stronger the antibacterial agent is.

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Classification Meanings


This is the arrangement of organisms into groups of various sizes on the basic of shared features


This is a form classification that focuses on physical similarities between different species, for ease of naming and identification


This is the classification of organisms by evolutionary relationships so that every groups shares a common ancestor

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Taxonomic Hierarchy

Domain - highest group. 3 domains--> Eukarya; Eubacteria; Archaebacteria

Kingdom - 4 kingdoms within the eukarya domain---> Animalia, plantae, fungi, protista

Phylum - for example- chroda - this includes vertebrates as well as animals with a primitive spinal cord

Class - for example; mamalia, insects, crustaceans

Order - for example; primates, rodents

Family - small taxonomic group - eg nominidae which includes humans, chimps, gorillas

Genus - smallest grouping of species; for example Homo --> humans are homo sapiens

Species - A specie usually consits of a group of individuals who can reproduce to create fertile offspring. Species must always include the genus they belong to; Homo sapiens

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Classification - Phylogeny

This is when species are grouped according to shared characteristics, the resulting taxonomy will often reflex their evolutionary relationships.

Superficial resemblance may arise in species from different branches of the evolutionary tree because two species may move to similar ecological niches, or one may be mimicking the other, for example, behavioural aspects

A disadvantage is that some species may also appear similar but they are actually related.

The key of this type of classification is looking for the sorts of common features that must be due to common ancestors and not evolutionary pressure

A good indicator of relatedness is the similarity of sections of non-coding DNA

Modern Systematics

This uses DNA, RNA and proteins to interpret the evolutionary relationships between organisms. Species contains organisms capable of interbreeding to produce fertile offspring

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Classification -Two Concepts

Biological Species Concept

It defines a species as a set of individuals who can repdroduce to produce fertile offspring

Two disadvantages are geographical separation and the fact that this only applies to organisms that reproduce sexually

Phylogenetic Species Concept

This defines a specie by its evolutionary lineage, where there are two lines diverge sufficiently they are could separate species.

A disadvantage is that it is difficult in desiding what constitutes sufficient divergence

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Classification - Binomial Name

A bionomial name is a name with two parts.

First part is the genus and the second word is the species.

For example; Human --> Homo sapiens    Tiger --> Panthera tigris

If a sub-species is identified, an extra name is added to the binomial species name. 

For exaple, the siberian tiger is known as Panthera tigris altaica 

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Biodiversity Meanings 1


It is a measure of how varied an ecosystem is and can be measured in terms of genes, species or habitats.

Genetic Diversity

It is a measure of variations there are in the genetic code between individuals of a specie or between different species.

Species Diversity

It is a measureof how many different species are present in an area and how many individuals of this species.

Habitat Diversity

It is a measure of how many different habitats are present in an area.

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Biodiversity Meanings 2


A simple level and an area in which species live; there is a range of of psysical, biological and envrionmental factors which a species can surivive


All organisms from the same specie


All of the populations of all species within a particular habitat

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Biodiversity - Species and Hybrids

What is a species?

A species is an organism which shares common morphological, physiological and behavioural characteristics.

For example:

- can interbreed

- produce fertile offspring


What is a hybrid?

A hybrid is a interbred specie.

 For example: A liger is a tiger and a lion.  A zonkey is a zebra and a donkey

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Measuring Biodiversity

It enables comparisions to be made in the same area at different times or at different areas. For example, comparing the biodiversity in one section of woodland with that of a similar type of woodland.

Species Richness - is the number of different types of species there are in one particular area. The greater the number of species there are, the greater the species richness. However, this type of meaurement does not take into account the number of individuals there are of a particiular specie.

Species Evenness - is a comparision of the size of the population (eg. the number of individuals) of different species within a particular area.

Species diversity within an area increaces as both species richness and species evenness.

An area has more biodiversity if the area has more species evenness.

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Biodiversity - Transects

Line Transects

A line transect is useful for examining the effect of a change in habitat on biodiversity; for example, the effect of a stream running through a field or wood.

A line is drawn through the area to be examined. Any species touching the line at fixed interval (eg. 1m) is recorded.

Belt Transects

A belt transect is similar to a line transect, but provides more detailed information.

Rather than simply recording the type of species touching the line, quadrats are taken at regular intervals along the line to indentify the number/density of the species along the belt.

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Miss Meera J


This is Unit 1 also!!!

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