Diffusion

What is diffusion?
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

Is diffusion a spontaneous process (no energy required)? Well, the answer is yes.
What are the factors affecting diffusion rate? One of the factors is temperature.

Diffusion is a spontaneous process (no input of energy required). This explains the below observations:
- Substances tend to spread from an area where they are more concentrated to an area where they are less concentrated
- Two or more substances can become evenly distributed (reach equilibrium) even without external interventions.

Concentration Gradient

First of all, what is concentration?
- Concentration = amount of substance (mass g/kg) / volume of fluid (cm3/ml)
- It is a measure of the amount of a substance in a specific volume.

The change in concentration between 2 regions is known as the concentration gradient.

In other words, the the concentration gradient between points A and B is difference in concentration between points A and B.

Relationship between concentration gradient and diffusion
- Particles diffuse down the concentration gradient.
- The larger the concentration gradient, the faster the rate of diffusion.

Applications of diffusion in Biology

This is a picture of an amoeba, a unicellular organism.

To stay alive, this organism needs to obtain nutrients and remove waste efficiently by diffusion.

"Chemical substances must be able to move from one place to another in order to keep the living organisms alive and growing."
For example, food substance that were absorbed need to :
- Move from one cell to another
- Move in & out of the cell
- Move from one part of the cell to another
One way which these movements would occur is by diffusion.
eg. Substance have to diffuse across membranes.

There are 2 types of membranes:
- Permeable membrane which allows ALL substances to pass through
- Partially permeable membrane which allows SOME substances to pass through; small particles can pass through, large particles cannot pass through

Diffusion across a permeable membrane :

Diffusion across a partially permeable membrane :

The visking tubing encloses a solution of starch while the beaker contains iodine solution.

Starch reacts with iodine to form a dark blue complex.



What type of membrane is the visking tubing? Explain. 
Partially permeable membrane. Iodine solution can enter the visking tubing while starch cannot pass through the visking tubing into the beaker of iodine solution.


Other example of diffusion in Biology include :
- Movement of carbon dioxide during photosynthesis
- Movement of oxygen and carbon dioxide in animals

Conclusion
- Diffusion is an important process where substances are moved without use of energy.
- It is the NET MOVEMENT of particles 9or molecules; or ions) from a region of HIGHER concentration to a region of LOWER concentration.
- Thus the movement is down a concentration gradient.
- The movement is random.
- The GREATER the concentration gradient, the FASTER the rate of diffusion.

Here's a quiz for you to try out!

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Ecology

Lithospere, hydrosphere & atmosphere are non-living components of the environment and are called ABIOTIC.
BIOSPHERE: Life supporting zone where the 3 zones meet, interact & make life possible

Lithosphere is the surface of the Earth, including aquatic systems, which contains most of the life.
Lower atmosphere - found to contain windblown organisms, seeds, and spores.

BIOTIC or living components include plants, fungi, animals and microbes living on Earth.
Constant interaction between the abiotic & biotic components of the biosphere results in the transfer of food and energy, making it a stable and dynamic SYSTEM.

A habitat is the physical place where a plant or animal (population) lives. It must supply the needs of organisms, such as food, water, temperature, oxygen, and minerals.
A population is a group of living organisms of the same kind living in the same place at the same time.
All of the populations in the same habitat interact and form a community.
A niche is the role and position of an organism (species) in the community. No two species can occupy exactly the same niche.
The community of living things interacts with the non-living world around it to form the ecosystem.
Ecosystems is a complex interaction of living and non-living processes e.g. as small as a puddle or as huge as the Earth.
Habitats that have similar climate and plants are called biomes.

------------------------------------ACTIVITY------------------------------------

PROCEDURE:
- Locate a small patch of land to examine.
- Use a string to form a circle to mark our study area.
- Record observations about your ecosystem. Include all living and non-living things.
- Record temperatures and other abiotic factors in your ecosystem.
- Turn over a small patch of the turf or vegetation. Observe what's beneath the surface. Replace whatever vegetation you have dug to the original state.

DISCUSSION:
- Consider the variety of living and non-living things in your ecosystem. Which was the largest population?
- How are the survival needs being met in your ecosystem? Air? Food? Water? Sunlight?
---------------------------------------------------------------------------------

Living things cannot exist alone, there must be a relationship between them. Living things are adapted to the environment where they live.
ECOLOGY is the study of how living things interact with each other and with their environment.
ECOSYSTEM consists of a community of living organisms interacting with each other and their environment to form a self-sustaining unit. The environment consists of non-living (abiotic) part and living (biotic) part.

Factors of that affect the ecosystem:

Light
- Affects many living organisms, not just plants.

Temperature
- Affects physiological activities of all living organisms

Water
- Essential for life
- Organisms may have specially adapted features for survival in places with a lot of or very little water.

Oxygen
- Most organisms are aerobes.

Salinity
- Important factor for aquatic organisms
- Also a factor for other organisms

pH
- May be influenced by photosynthetic activity of aquatic plants (freshwater)
Acids pH : 1 - 6.9
Alkali pH : 7.1 - 14.0
Water (neutral) : pH 7.0

--------------------BIOTIC FACTORS----------------------

1. Symbiosis
- a long-term relationship between two different species "living together". The relationship varies in population, can be mutualism, commensalism & parasitism.

Mutualism
- Each population benefits. The interaction is necessary for the survival and growth of each species
+ / + relationship

Commensalism
- One population benefit; the other is unaffected
+ / O relationship

Parasitism
- One population benefits (parasite) while the other is harmed (host). The interaction is necessary for the survival of the parasite.
+ / - relationship

2. Competition
- Both population compete with each other for limited resources in the same ecosystem; both species are adversely affected by the relationship.
Interspecific (a form of symbiosis) or
Intraspecific (same species) competition
- / - relationship

3. Predation
- One population feeds on the other. The interaction is necessary for the survival of the predator.
+ / - relationship

FOOD CHAIN
- A series of organisms through which energy is transferred in material form.
- Carbon compounds move through the flood chains.

- All the energy in an ecosystem comes from the SUN.

The study of food chain helps in understanding of food relationships and interactions among various organisms in an ecosystem.

By studying food chain, we can follow the basic mechanism of transfer of food energy and nutrients through various components of nature.

Food chain helps us understand the movement of toxic substances in an ecosystem and the problems of their biological transfer of food along with toxins substances.

Non-cyclical Nature of Energy Flow in Biological Systems
- Energy flows in one-direction (non-cyclical) and it is either utilised or lost into the surroundings but cannot be recycled.

What happens to the light that falls onto a leaf?

Unidirectional flow of energy
- The amount of available energy in food web decreases with each successive leve.

Food consumed = growth + respiration + heat + egesta (faeces) + excreta (urine)

Only about 10% of the energy is stored as new tissues and is available for transfer to next feeding level.
90% of the energy is lost because some food may not be eaten, or passes through the body without being digested and a lot of the energy is used in respiration.

The total mass of living organisms that can be supported at each higher level also decreases.
The shorter the food chain, the greater is the available food energy.

Decomposers are detritivores that recycle organic matter back to inorganic nutrients (carbon, nitrates) in ecosystems. E.g. fungi, bacteria
Detritus feeder acquire nutrients from dead animals/plants or animal waste products. E.g. certain beetles, earthworm, termites, bacteria, fungi.

Cycling of Nutrients in an Ecosystem

Carbon Cycle and Nitrogen Cycle

Ecological Pyramids

- Pyramids of numbers
  - indicate the relative numbers of individuals at each level

- Pyramids of biomass
  - the dry mass of all the organisms at each trophic level may be estimated

- Pyramids of energy
  - the total energy utilized at each trophic level

CARBON CYCLE

- atmospheric CO2 is 0.03% (main source) important component of all living organisms.
- only plants can take in CO2 & convert it to organic compounds
- carbon compounds move through the food chains
- CO2 is returned to the atmosphere through respiration decay activities also release CO2
- Carbon may be trapped in limestone and fossil fuels

Microscopy

Light Microscope
- Found in most schools
- Uses compound lenses to magnify objects
- The lenses bend or refract light to make the object beneath them appear closer
- Oil immersion lenses can improve quantity of focus and magnification
- Common magnification : 40X, 100X and 400X

Stereoscope
- Allows binocular (two eyes) viewing of larger specimens
- Magnifies 10X to 20X
- Used for thicker specimen
- Creates 3D view of specimen

Guidelines on handling the microscope
- Always carry with 2 hands
- Use lens paper for cleaning
- Do not force knobs
- Always store covered
- Keep objects clear of desk and cords

Magnification
- 3 magnifications : Scanning (Red), Low (Yellow), High (Blue)
- Ocular lends (eyepiece) has a magnification
- Total magnification = ocular lens X objective lens
- We can see better details with higher magnification powers.

Cell Structure and Function

Cell Theory
- All living things are made up of cells.
- Cells are the smallest working units of all living things.
- All cels come from pre-existing cells through cell division.

Definition of cells
A cell is the smallest that is capable of performing life functions.

Two types of Cells
- Prokaryotic
- Eukaryotic

Prokaryotic
- Do not have organelles (specialized structures in cells) surrounded by membranes
- Few internal structures
- One-celled organisms eg. bacteria

Eukaryotic
- Contain organelles surrounded by membranes
- Most living organisms eg plant, animal, fungi

Cell Parts

Organelles - specialized structures in the cell

SURROUNDING THE CELL

Cell Wall

- Most commonly found in plant cells & bacteria

- Surrounds the cell membrane

- Rigid structure that maintains the shape, supports & protects cells

Cell membrane
- Selectively/partially permeable membrane of cell that controls movement of substances in and out of the cell.
- Permeable to small molecules and small proteins only

INSIDE THE CELL

Nucleus
- Contain chromatins that control cell activities
- Chromatins contain DNA which is genetic material
- DNA contain instructions for traits & characteristics and to carry out the cell's function
- Separated from cytoplasm by nuclear membrane

Cytoplasm
- Gel-like mixture
- Surrounded by cell membrane
- Contains organelles

Mitochondria
- Referred to as the "powerhouse" of the cell.
- The food we eat is transformed into energy (ATP) for the cell and our bodies.

Endoplasmic Reticulum
- An interconnected network of tubes and vesicles
- Synthesis of proteins, fats, steroid
- Transports materials around in cell
- Smooth type: lacks ribosomes
- Rough type (in picture) : ribosomes embedded in surface

Ribosomes
- Each cell contains thousands
- Make proteins
- Found on endoplasmic reticulum & floating throughout the cell

Golgi Bodies
- Works closely with the ER
- Primary function is to process and package complex molecules such as proteins and fats that are made by the cell
- Bring these products to the surface of the cell where they can be secreted
- Other secretions include hormones, antibodies and enzymes

Lysosome
- Contain digestive enzymes
- Digest excess or worn-out organelles, food particles and engulf bacteria or viruses
- Also help repair worn-out plasma membrane
- They also provide sugars, amino acids and bases which are the foundation of macromolecules
- Cell breaks down if lysosome explodes

Vacuoles
- Membrane-bound sacs for storage, digestion, and waste removal.
- Central large vacuole-help plant cells maintain shape
- Food vacuoles: formed by phagocytosis
- Contractile vacuoles (in freshwater protist): pump excess water out of the cell

Chloroplast
- Usually found in plant cells
- Contains green chlorophyll
- Where photosynthesis takes place
- Converts light energy into chemical energy in glucose

Difference in plant cell and animal cell
- Chloroplast appears in the plant cell while it does not appear in the animal cell
- The plant cell has a large central vacuole while the animal cell has many mini vacuoles.
- The plant cell has a cell wall but an animal cell does not have a cell wall. Therefore, the plant cell has a fixed shape while the animal cell has an irregular shape.

Classification!

Why do we need to classify organisms?
Hmmm.....Maybe to easier call them in a more general terms? Or to show that the organisms that are classified together have common characteristics or traits? O.O
- Accurately & uniformly names organisms
- Prevents misnomers such as starfish & jellyfish that aren't really fish
- Use same language (Latin or some Greek) for all names

How many species are there?
- There are 13 billion known species of organisms.
- This is only 5% of all organisms that ever lived!
- New organisms are still being found and identified.

What is classification?
- Classification is the arrangement of organisms into orderly groups based on their similarities
- Classification is also known as taxonomy
- Taxonomists are scientists that identify & name organisms.

Early Taxonomists
- 2000 years ago, Aristotle was the first taxonomist
- Aristotle divided organisms into plants & animals
- He subdivided them by their habitat.
- John Ray, a botanist, was the first to use Latin for naming
- His names were very long descriptions telling everything about the plant.

Carolus Linnaues (1707-1778)
-18th century taxonomist
- Classified organisms by their structure
- Deveoped naming system still used today.
- Called the "Father of Taxonomy"
- Developed the modern system of naming known as binomial nomenclature
- Two-word name (Genus & species)

Problems in Classifying Organisms
- Species are always changing
- Inter-breeding

Standardized Naming
- Binomial nomenclature used
- Genus species
- Latin or Greek
- Italicized in print
- Capitalize genus, but NOT species
- Underline when writing

Rules for Naming Organisms
- The International Code for Binomial Nomenclature contains the rules for naming organisms.
- All names must be approved by International Naming Congresses (International Zoological Congress)
- This prevents duplicated names

Classification Groups
- Taxon (taxa-plural) is a category into which related organisms are placed
- There is a hierarchy of groups (taxa) from broadest to most specific
- Domain, Kingdom, Phylum, Class, Order, Family, Genus, species

Domains
- Broadest, most inclusive taxon
- Three domains
- Archaea and Eubacteria are unicellular prokaryotes (no nucleus or membrane-bound organelles)
- Eukarya are more complex and have a nucleus and membrane-bound organelles

Taxons
- Most genera contain a number of similar species, with the exception of Homo that only contains modern humans
- Each successive classification category or taxon contains more different types of organisms than the preceding category.

Easy way to remember the order of Classification Group! :)
King                     (Kingdom)
Phillip                  (Phylum)
Came                    (Class)
Over                     (Order)
For                       (Family)
Gooseberry           (Genus)
Soup                    (Species)

Scientific Investigation

Lemme give you some information about what you need to know when you do an experiment! :)

What is an/a...:

Term	Meaning
Aim	What you want to find out (It should be a statement)
Hypothesis	Predicted answer, no cause and effect answer (must be in absoute terms
Independent Variable	Variable that is being changed by the investigator
Dependent Variable	Variable that changes as a result of a change in independent variable
Constants (Controlled variable)	Factors that remained unchanged throughout
Control Group	A group which does not have anything that the experimental group has. In place of the independent variable, this group adds something which does not have much impact on the things.

Observing Primates

Today, we watched a video called "Observing Primates". We were supposed to observe how the gorilla moves about using their arms, legs, hands, and feet and generate questions on how they move. It is a continuation of yesterday's activity.

Here are some of our observations:

- When walking:
   - Hands are partially clenched, knuckles touching the ground
   - Hunched-back
   - Arms were bent at a certain angle
- Generally:
   - Feet look like hands (big toe is very far away from the rest of the toes)
   - Long arms (even longer than their legs)
   - Walk with four limbs sometimes, walk with two limbs sometimes
   - Male gorillas pumping/hitting their chests (once in a while?)

Here are some of our questions:
- Wouldn't their hand hurt if they support themselves with their clenched hands while walking?
- Why must they walk using four limbs when they are able to walk using two limbs?
- Wouldn't it be difficult to move with their 4 limbs in such a position?
- Why do male gorillas pump/hit their chest?
- Why they move on fours sometimes, twos at other times?
- Why is there a large space between the big toe and the rest of the toes?
- Do gorillas swing on trees?
- Why are their arms longer than their leg?
- Why is the skin so rough/horny (cough cough, its a scientific term)?

Since we had so many questions, we narrowed them down based on whether they are testable and we came down to 2 questions:
- Why on fours at time, twos at other times?
- Why are their arms longer than their legs?

To help us understand what does it mean being able to be testable, we carried out a simple exercise using the following 2 questions:
- What is the importance of an opposable thumb for the way in which humans use their hands?
- Without using your thumbs, can you unpin your name tag from your uniform?

The first question was too general as there is a wide variety of objects and items that we can test with. However, for the second question, it was much specific and therefore, testable.


The Chimp Scientist ( Jane Goodall)

A short introduction of who she is. Dr. Jane Goodall started to observe and study the chimpanzees of Gombe Stream in Tanzania, Africa, more than 30 years ago, opening a whole new world of knowledge to science. Because of her investigation, her work is recognized as one of the great contributions to science made during the 20th century.
After reading about her investigation about chimpanzees, I felt that she was very brave to take the first step to scientifically talk about an animal's mind or personality or to give funny names to their subject. She is also very patient as to spend her time just observing each and every move of the chimpanzees and noting them down in her own way in her notebook so that she can write quickly and understand them later. Due to the work of Dr. Goodall and other scientists in related fields, we now recognize that many intellectual abilities once thought to be unique to humans are also present in animals. One such observation is the ability to not only use tools, but also recognize a need for them. She also found that chimpanzees were also very clever. Because of Dr. Goodall's long-term study and careful observations, we are now able to construct our understanding of the true nature of chimpanzees and knowledge about our closest living relative makes it possible to learn more about our common evolutionary heritage.