Specialised Cells, Evolution, 23/7/2012

4 types of specialised cells:

~RBC (Red Blood Cells)
~Xylem vessel (xylem cell)
~Root Cell
~Intestinal cell

Red Blood Cells

Structure:
~It is biconcave shaped
~No nucleus so gotten rid off by the liver
~can change shape (flexible) 
~Has haemoglobin

Function:

~The biconcave shape increases the surface are to volume ratio so more oxygen can be diffused as more Red Blood Cells can be compacted into a certain amount of space.
~Haemoglobin allows transportation of oxygen and not having a nucleus allows more haemoglobin to be inside the cells so more oxygen can be transported.

How does the biconcave shape help in increasing S.A. to volume ratio?

Red blood cell--LARGER surface area compared to other cell that has same volume.









Xylem Vessel

~Three types of cells: Xylem parenchyma cells and fiber cells and tracheary elements.
~The first 2 cells provide structural support for TE.
~TE are dead when they mature and act like pipes to allow water and dissolved minerals to flow through them.
~The support is provided by secondary cell wall thickenings, which form in distinctive patterns mostly rings to provide maximum structural support. the cells are arranged end to end.

They are made of lignified cell walls and the secondary cell walls are made of lignin which is a type of hard glue.

The xylem vessel is used for 2 functions:

~Transport system (transports minerals and water)
~Support

Root Cell

~has a long and narrow protruding end which increases the surface area to volume ratio, enabling the root hair cells to absorb more water and mineral salts from the soil.

Intestinal cell

Epithelial cells in the small intestine are a type of brush border cell (covered in microvilli). These cells are covered in microvilli to increase the surface area to volume ratio thus making them more efficient.


Uses:

• Ion uptake
• Water uptake
• Sugar uptake
• Peptide and amino acid uptake
• Lipid uptake
• Vitamin B12 uptake
• Reabsorption of unconjugated bile salts.
• Secretion of immunoglobulins

Most of this information was from our class google docs on specialized cells.

Lab Report for Scientific Investigation practical (mealworm experiment)

1.   What do you want to find out? (Aim/Purpose/Research question)

The aim of the experiment is to find out whether mealworms would choose to live in dark or bright conditions.

2.   What is the tentative explanation of your research question? (Hypothesis)

The mealworms will mostly remain in the dark.

3.   In an investigation, there is only one variable to be changed. Which variable will you change in this investigation? (Independent Variable)

The independent variable is the presence of light.

4.     All the other variables must be kept constant. List a few important variables that will affect the results greatly. (Controlled Variables)

The controlled variables are the number of mealworms on each side (bright and dark) initially, the amount and type of food on both sides.

5.     What results will you measure? (Dependent Variable)

The dependent variable is the number of mealworms on each side at the end of the experiment.

6.     State the assumptions that you have made

The assumptions are the dark side has no exposure to light, the bright side has no dark patches, there is an equal amount of food on both sides and all 4 mealworms are similar. If there are more mealworms on a particular side, the mealworms prefer that particular side.

7.     List the materials and apparatus that you will need to carry out the investigation.

(Materials and Apparatus)

Materials and Apparatus:

C  4 mealworms C  A plastic container C  Some food for the mealworms C  Strong light C  Some cloth C  A shelf with ample space to keep the container underneath

C  _______________________ C  _______________________ C  _______________________ C  _______________________ C  _______________________

8.     List the steps that you will take to carry out the investigation. (Procedure) Include drawing of setup.

Procedure:

Step 1: Place the food in the container evenly.

Step 2: Place half the box under strong light and place the cloth over the remaining half. To ensure that no light enters the dark portion, shift the dark half under the shelf.

Step 3: Place 2 mealworms onto each side of the container.

Step 4: Observe their movements in a daily interval basis over 3 days.

9.     Data collection and organization. (Results)

The data can be presented in the form of tables and/or graphs.

Results: After 3 days, 3 of the 4 mealworms were in the dark section of the box. They have moved towards the light but then avoided it later.

10.   Explain what your data means. (Data Analysis)

What did you observe and give reasons to your observations.

Data Analysis: This means that the mealworms prefer dark conditions as there are more mealworms on the dark side and if there are more mealworms on a particular side, then they prefer that living condition

11.   What can you deduce from the discussion of your data analysis? (Conclusion)

State if your data support your hypothesis? If not, what would you do? In other words, how can you further improve your design? What do you think have been carried out incorrectly and affected the data collected?

Conclusion: My hypothesis has been proven right and Mealworms prefer dark to bright conditions.

Drawing of a mealworm:

                                                                   

 Characteristics of the mealworm:

Number of segments: 12

Length of mealworm: 3.5cm

Colour: Brown

Other distinguishable characteristics: Head and end of body is darker in colour. It has 6 legs, 2 antennae and distinct divisions that show its segmented body.

~End of lab report~

Classification, Evolution, 16/7/2012

Why do we need to classify organisms?


~Easier to compare similarities and differences between organisms
~Find certain organisms using their characteristics
~Accurately and uniformly name organisms
~Prevent misnomers (that is, misleading names) such as starfish and seahorse that are not really fishes or horses
~Use standard language (Greek/Latin) for all names


What is classification?


Simply said it is the arrangement of  organisms into standard groups based on similarities
It is also known as Taxonomy


Some facts on biodiversity:


There are 13 bil. known species of organisms which is 5% of all organisms ever lived. This number is growing as new organisms are still being found and identified!




Binomial Nomenclature--The current system of classifying invented by Carolus Linnaeus.

Scientific name of all organisms: Genus(start with caps) species(small letters)

Italicized in print, underlined in writing

e.g. American robin's scientific name--

(in print): Turdus Migratorius
(in writing): Turgus Migratorius

Taxon (pl. taxa) is a category into which related organisms are placed.

Hierarchy of groups (taxa) from broadest to most specific

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

3 Domains, broadest, most inclusive taxon:

Archaea and Eubacteria--Unicellular prokaryotes (no nucleus or membrane-bound organelles), Eukarya--more complex and hae a nucleus and membrane-bound organelles


Most genera contain a number of similar species, with the exception of Homo, which contains only modern day humans

Each successive classification category or taxon contains more different types of organisms than the preceding category

Classifying Humans...

Domain Eukarya --Cells with nuclei
Kingdom Animalia --Multicellular
Phylum Chordata  --vertebrates
Class Mammalia --Hair, mammary glands
Order Primates --Adapted to climb trees
Family Hominidae --Adapted to walk erect
Genus Homo -- Large brain to use
Species Homo sapiens --characteristics of modern day man.


This is just an example. There many other ways to classify organisms even though they have the same scientific name.

Cell structure and function, 17/7/2012

Learning Outcomes:


~Cell is the main unit of life
~Identifying and stating function of main organelles in cell like nucleus, nuclear membrane, chromatin, endoplasmic reticulum, cytoplasm, etc.
~Identify main organelles in diagrams
~Compare and contrast plant and animal cells
~explain how specialised cell structure is related to function


Cells
found in ALL living things  and they come from pre-existing cells via cell division.


A cell is 3D and it can be cut longitudinally and laterally.


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


Some examples:
~Amoeba proteus
~Bacteria
~Nerve cell

A prokaryotic cell
from http://library.thinkquest.org/C004535/media/prokaryote.gif 

~Red Blood Cell


2 types of cells


~ Prokaryotic
~ Eukaryotic


Prokaryotic
~Do not have organelles surrounded by membrane
~Few internal structures
~unicellular organisms belong in this category


Eukaryotic
~Contain organelles surrounded by membranes
~Most living organisms (multi-cellular) such as animal, plant, fungi belong in this category.




Parts of a cell


Cell wall
~Most commonly found in plant and bacteria cells (not in animal cells)
~Surrounds the cell membrane
~Rigid structure that maintains the shape, support and protects cells
~Permeable to small molecules and proteins only
~FULLY PERMEABLE


Cell membranes


~Selectively/Partially permeable membrane of cell that controls movement of substances in and out of cell


*Cell membrane is a phospolipid bilayer. This layer is made up by Hydrophilic 


Nucleus
~Contains chromatin that controls cell activity
~Chromatin contains DNA (Deoxyribonucleic acid) 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
~"Powerhouse" of the cell
~Food that is eaten is transformed into energy (ATP--Adenosine5'-triphosphate) for cell and bodies.


(*ATP transports chemical energy in cells for metabolism)


Endoplasmic reticulum
~Interconnected network network of tubes of tubes and vesicles
~Synthesis (i.e. ) of proteins, fats, steroids
~Transports materials around cell
~Membrane bound organelle


2 Types
Smooth type (no ribosomes)
Rough type (ribosomes embedded in surface)

Ribosomes
~Small structures that are found in thousands in the cell (either floating throughout the cell or on rough endoplasmic reticulum)
~Make proteins (with the aid of mRNA)


Messenger sends proteins from nucleus via nuclear pores despite endoplasmic reticulum connection with nucleus 


mRNA- Messenger RNA is made from DNA in chromatin which is sent to the ribosomes to be translated into proteins (comes from amino acids)


Golgi Apparatus& Bodies


Note: Apparatus and bodies can be used interchangeably. Apparatus is used when cut longitudinally and bodies used when cut laterally.


~Works with the Endoplasmic Reticulum
~Main aim is to process and package molecules such as proteins and fats made by cell
~Brings these products to the surface of the cell where they can be secreted
~Other secretions include hormones, antibodies and enzymes


Lysosome


It aids in digestion and defense in/for cell
~Contain digestive enzymes
~Digest excess or worn out organelles, food particles, or engulf bacteria or viruses
~Helps repair worn-out plasma membrane
*It repairs worn-out membranes by fusing with the membrane.
~They also provide sugars, amino acids and bases which are the foundation of macromolecules
~Cell breaks down if lysosome explodes. 
*This is called necrosis, which occurs when one gets injuries.
*apoptosis is the more subtle version of necrosis, where it takes place in normal circumstances


Vacuoles


~Membrane-bound sacs for storage, digestion and waste removal
~Central large vacuoles help plant cells maintain shape
~In animal cells, vacuoles are small and numerous in number
~ Food vacuoles are formed by phagocytosis
*Phagocytosis on how the food vacuoles are formed:
When a food particle enters a cell, an organelle called the cytostome extends it "2 arms" around the particle like a membrane, thus forming a food vacuole.


Chloroplast
~Usually found in plant cells
~Contains green chlorophyll
~where photosynthesis takes place
~Converts light energy to chemical energy in glucose 

The differences between Plant cells and Animal cells

Plant Cell                                            VS.                                   Animal Cell

~A central large vacuole                                                                        ~Multiple vacuoles that are small

~Contains Chloroplasts                                                                          ~ No chloroplasts present

~ Cellulose cell wall present                                                                  ~ No cellulose cell wall present

~Regular shape                                                                                      ~ Does not have a regular shape




*In plant cells, since it mostly consists of fluids, the chloroplasts will move toward the sunlight at ALL times in what is called cytoplasmic streaming.

Harvard VPA, HBL, 13/7

Some screenshots taken during Harvard VPA:

This was the 2nd assessment on the Silence of The Bees. A screenshot was not taken during the 1st assessment: There's a new frog in Town.

Scientific Investigation 5/7/2012~ A practical on Ethology, part of Evolution

OBSERVING LIVE SPECIMENS: Case Study on...MEALWORMS

Pre experiment Study: What is Ethology?

In a nutshell, Ethology is the study of animal behaviour. So today's experiment is on the study of mealworms' behaviour.

Using the following diagram, we can formulate an experiment and put it into place to observe mealworms behaviour.

Stage 1: What is needed for an experiment?

Planning an Experiment requires...

1) A general question leading to a specific question with assumptions. The questions must be testable and valuable.

2) The aim followed by the hypothesis. the aim is a statement on what you want to find out and the hypothesis is a detailed prediction with the possible explanation for the expected result. It must be specific and not be a Cause and Effect statement.

3) Variables: namely, Independent (the variable changed based on what one wants to test), Dependent (The variable changed due to change in independent variable, also known as the results) and the Constants (Unchanged factors, remain the same)

4) Control and experimental groups

Control: Serves as a basis for comparison of results, does not have the independent variable, but all other variables.

Experimental: Has ALL variables including the independent variable, the aim you want to find out.

5) The number of subjects: the number of guinea pigs for your experiment must be the same. and testing on all of them is different from...

6) The number of times test takes place.

How many times you conduct the experiment.

Stage 2: Pre-experimental observations on the mealworms (except for taste)

Sight: Brown, small and thin worm-like shape, many distinctly segmented parts on body, 6 legs, 2 antennae (feelers)

Smell: Odourless

Sound: Not really many sounds

Feel: Smooth, can feel the deep divisions very distinctively

The mealworm drawing:

Stage 3: Carrying out some experiments

Experiment 1: Can the mealworms HEAR?

Aim: To find out if mealworms can respond to sound.

Hypothesis: We believe that the mealworm can hear and will respond to sound as sound (or vibrations) are important to ensure that it can get its food.

Procedure:

1) Have 2 groups: Control and Experimental, where each group has 4 mealworms.

2) Control--Assumption of No sound exposure. Observe movement for 5 minutes

3) Experimental--Exposed to the sound of the castanets for 5 minutes Observe movement.

4) Record observations.

Results:

For control group: Mealworms moved in random direction, not moving to anywhere in particular.

For experimental group: Moved towards source of sound, even if location changes.

Hypothesis proven RIGHT!

Experiment 2: Can the mealworms SMELL?

Aim: To find out if mealworms can respond to smell.

Hypothesis: Mealworms can respond to smell as they also need smell to look for food.

Procedure:

Once again the same 2 groups of mealworms who will be our KIND guinea pigs. They are in an air tight container with holes for air to enter.

Control: Assumption that they are Exposed to NO SMELL. 

Experimental: Placed with a vinegar soaked cotton wool piece.

Observe and record movements for 5 minutes.

Results: 

Control group: No change in movement. Random movement.

Experimental group: Moved towards cotton wool before turning away from it.

This once again proves our hypothesis right. However, we were kind of surprised that the mealworms actually moved AWAY from the vinegar since we thought that they would actually not mind vinegar...

Experiment 3: Does it prefer light or dark? Or, can the mealworm SEE?

Aim: To find out how mealworms react when placed under light.

Hypothesis: We think that the mealworms will move away from light. We're not sure why, but it is probably due to the fact that most worms don't really like light. 

Procedure: the same 2 groups of mealworms.

Control group not exposed to any light, placed in darkness.

The experimental group is also placed in darkness, but there is always a patch of light.

Observe movement for 5 minutes.

Results:

Control group: No change in movement, always in random directions.

Experimental group: Moves towards light, but once senses light moves away.

Experiment 4: Can the mealworm feel?

Aim: To find out how mealworms react when being touched by something.

Hypothesis: It will mostly squirm away from most objects.

Procedure: The same 2 groups of mealworms.

Control group is not being touched by any object. However experimental group is being touched by cotton bud and paintbrush.

Observe movement for 5 minutes.

Results: 

There was no difference in the movement of the control experiment. For the experimental group, the mealworms mostly backed away from the objects, although, for the first time, they actually climbed on the cotton bud, then they squirmed away from it.

Modifying your experiment:

The experiment chosen: Light

How would I modify it?

For the experimental setup, ensure that 1 part of the box is in total darkness while the other part is in bright light. Also, one can actually find out if they prefer dak or light by simply counting the number of mealworms in each side of the box in the end, or by just observing how they move.

Is it alive? 27/6/12~a practical, on Evolution

IS IT ALIVE?

Before the Practical...

Some tings to take note of...

1) Characteristics of Living things
2) Conditions to support life

1) Characteristics that have been come up with...

~Ability to reproduce
~Grow
~Die
~Respond to changes (stimuli) in environment (also known as adaptation)
~Evolve
~Move
~Have hereditary information
~Made up of protoplasm (not Cytoplasm but P-R-O-T-O-P-L-A-S-M)
Protoplasm-> Living matter=Cells
*~Excrete liquid waste from metabolism
~Respire
the equation is: O2+C6H12O6-> H2O+CO2+large amount of energy.

In other words, oxygen+glucose-> water+ carbon dioxide+ lots of energy.

* plants do not release solid waste. the term excrete is used for liquids/fluids only.
The term for solid waste is: egestion

2) Condition needed...

Air, food, water, shelter (not all), warmth, energy, adaptation to changes, and light for plants

Also, ~Homeostatis (ability to control) ~Continuity (of own kind) ~Development (growth) and ~Ecology (interactions with other living things) are needed

WARMTH is necessary for all living things because it is needed to carry out all life processes. If there was no warmth then particles would not be able to move and the particles would be just FROZEN. so warmth is necessary.

On to the pre-practical question:

Designing an experiment to test if an object is LIVING.

~Characteristics to test--Respiration
~How to carry out the experiment.
~What evidence will show it's living--Chalky limewater
~Can you infer from evidence that it is living?--Yes, for respiration gives out CO2 and if limewater is chalky means CO2 has been given out so substance is living.

Experiment

Place substance in glucose solution filled container. Place it in an ait tight container with limewater inside. Check after a few hours to see if limewater has turned chalky due to presence of carbon dioxide. This shall prove that the substance is living.




Practical Question:


Testing for life in objects.


Here are the results when substance was put in WATER.


Substance:           Physical appearance:    Changes after 10min:   Evidence/Inference to show life:

A                        coarse and grainy         no change, settles to bottom.

B                        smooth and powdery     clumpy, settles to bottom, cloudy       respiration

C                         hard, transparent, around        expanded                                 growth
                           2mm diameter                

D                        hard and tiny, brown          settles to bottom, no change
                           particles, negligible
                           diameter

E                       Brown, small particles       suspended all over water, no change.


Same was observed for glucose, except for B, where bubbles were observed and glucose was more cloudy.


Pause to Ponder:

Why was glucose used?

Glucose is used for respiration as a form of food. Therefore, to supplement the substances with food, glucose was used.  


3rd part:

Substances placed in soaked cotton wool in petri dish and left for observation.

No changes observed in any of the substances except for D, where plants had sprouted from the particles (now to be confirmed as seeds).

4th part:

Observation of substance E under salt water through microscope.

Picture of substance E in salt water under microscope:

some tadpole like creatures swimming (wriggling) about, past molecules.


Revelation of substances...
E: Brine Shrimp
D: Seeds
C: Water Babies
B: Yeast
A: Sand/Gravel

will continue soon..bb 4 now! :)

Get a Grip! 26/6/12, Evolution

Activity 1: to observe different way of holding objects with our hands

Some interesting words were used to describe ways of holding objects. Here are a few discussed in class.

1) Gripping with thumb and index (pinch)

2) Pinching with index and middle (scissors)

3) 4 fingers at 1 side of object, thumb at other side.

4) 4 fingers around object (small/thin/long) thumb curled and in contact with other side.

5) palm and 4 fingers curling around object.

6) 2 palms touching (scooping)

7) same as 2) but using 4th and last finger

Activity 2: observing and drawing of how I hold my object.

(shown at right)

description of the object: 4 fingers curled around object and thumb curled and on top of the 4 fingers.

My description was accurate enough for my partner to guess how I had held the object. 

Activity 3: Observation of how gorilla moves about and physical appearance of arms, legs, hands, and feet 

This is with reference to the video: OBSERVING PRIMATES

Observations made and differences highlighted between humans' and gorillas' limbs:

FEET: Gorilla has huger gap between big toe and other toes compared to humans.

HANDS: Gorilla has wider digits and "furrier" hands compared to ours.

Some motions of the gorilla: The gorilla moves on fours, with its fists clenched. However, sometimes, it walks on twos. Its limbs, though,  are bent and swing to and fro.

WHY are there such differences?

The black hands (or outer covering) is to enable it to camouflage in its surroundings, so that its predators/prey will not find it.


As for the feet, before we go on, there is one thing to be mentioned here.


Humans have what are known as opposable thumbs. This is because the thumb can only move in the opposite direction of the other 4 fingers. Likewise, this feature is present in the gorillas and most primates. This adaptation is useful to grab items (or stuff, as I prefer to word it). However, some monkeys have prehensile tails (a tail adapted to hold STUFF) to carry out the above mentioned action. 


Moving on...


Now, since gorilla has to grasp on branches and move, therefore, they have opposable toes to grip the branches firmly in order not to lose their balance. 


Enough about gorillas, so let's moo-ve on...


Activity 4: Questions on how primates move.


Some questions to think about...


1) If other primates have opposable toes to grasp onto branches, then why do they need a prehensile tail to grasp onto objects?
2) Why do gorillas need to move in fours when they can easily move in twos like use humans?
3) Why do gorillas have to clench their fist and walk in fours, rather than placing their palms flat on the ground?


Well that's about all for now. Will continue soon so bb :)

Hi :D

An warm welcome to the reader...

Hello there. I am a self confessed freak who loves math and science and HP (not the printer brand but Harry Potter). I currently work/study/um do stuff at Hogwarts School of Witchcraft and Wizardry (in my dreams, in reality, I study at Raffles Girls' School). Well before I digress further, this, as you can see, is my science journal, so yep, you'll only see stuff about science here..well hope you have lots of fun reading this journal...so bye for now. :)

~Swathi