Regents Review Part D The State Labs

Diffusion Through a Membrane

Diffusion Through a Membrane Concepts You Must Know: The dialysis bag is the “cell” Diffusion moves materials from high to low concentration, expending no energy Only small molecules with go through the membrane (selective permeability) … starch is too big a molecule

Diffusion Through a Membrane Concepts You Must Know Benedict's solution tests for sugar…heat it and it turns red/orange (positive for glucose) Iodine tests for starch…turns blue/black in starch Water is used as a control for the indicators The diffusion of water is osmosis

Diffusion Through a Membrane Procedure: Make a dialysis tube “cell”…the tube represents the cell membrane Pour glucose and starch into the cell Add iodine to the water outside the cell The cell should turn blue/black Test the water outside the cell for glucose

Diffusion Through a Membrane Observations and Questions: Where did the iodine go? Where did the starch go? Where did we use Benedict’s? Where did the glucose go? The iodine diffused into the cell as evidenced by the liquid in the cell turning black due to the presence of starch inside The starch remained in the cell or else we would have seen the water outside the cell turn black – the starch molecules are to large to fit through the cell membrane We used the Benedict’s to test the water outside the cell for the presence of glucose. The water tested positive because the glucose diffused out of the cell.

Diffusion Through a Membrane Observations and Questions: Why must we digest starch before we can use it for energy? Why do they serve free salty pretzels in a bar? Starch molecules are too large to fit through your body cell’s membranes - we must break them down into smaller molecules (digestion) to get them into the cells The salt in you mouth makes the environment salty which causes the water in your mouth’s cells to diffuse out of the cells – making you feel thirsty. Thirsty customers buy more drinks!

Diffusion Through a Membrane

Biodiversity

Biodiversity Concepts you must know: Organisms with structural or molecular similarities may be related In order for a species to be successful and survive it must contain variety (diversity) Proteins and enzymes are produced as a result of an organism’s genetic code sequence

The DNA code is transmitted from Biodiversity The DNA code is transmitted from DNA → mRNA → tRNA Base pair codes are as follows: DNA A --T “always tired” C -- G “constantly grumpy” m and t RNA A –U “always ugly”

Biodiversity Amino acids are building blocks of proteins Molecular similarities are the most important evidence of closely related organisms Organisms evolve much like the branches on a tree Biodiversity ensures genetic variation

Biodiversity Biodiversity increases stability in an ecosystem Endangered species hold medicinal, agricultural, ecological, commercial and aesthetic value. They must be protected for future generations

Biodiversity Questions: What activities by humans could endanger plants? Why is Botana Curus so important? How can it be saved? Why would you not want to save Botana Curus from extinction? Air, water and land pollution, development, bringing in invasive species A cure for cancer was developed from an extract of Botana Curus – the area can be legally protected from development or reproduced in a protected environment. It might be too expensive or there might be other plants (not as rare) that can also be used as a cure.

Making Connections

Making Connections Concepts you must know: Resting pulse rates vary with individuals. By collecting data, scientists can help to answer questions they have proposed. Pulse rate increases under physical or emotional stress. Increase in activity produces muscle fatigue. Use Scientific Method to solve a problem that you have postulated.

Making Connections Be able to prepare a designed experiment with the following format: Title Hypothesis Method/Materials Data collected Conclusions Suggestions for improvements Suggestions for further research

Darwin’s Beaks of Finches

Beaks of Finches Concepts you must know: Certain adaptations give some organisms an advantage to survive. The environment “naturally selects” which organisms are best suited (fittest) to survive and reproduce. ** In this lab, the type of seeds (food) was the selecting agent in the island environment**

Beaks of Finches Those organisms that survive and reproduce pass these favorable traits on to the next generation. This gives their offspring an advantage to survive. Competition for resources (food, water, mates and territory) stimulates the struggle for survival.

Beaks of Finches Questions: What other traits will help finches survive besides the shape of their beaks? What type of beak will be a favorable adaptation to catch mice on the island? Speed, good eye sight, aggressiveness A large sharp, strong beak

Beaks of Finches Define the following terms: Variation – Competition – Struggle for survival – Adaptation – Environmental selecting agent - Genetic mutations and sexual reproduction result in different combinations of traits that give species differences (variation) When niches overlap, organisms have to fight for food, mates or territory. When there is competition, the strongest will survive (survival of the fittest) or those best adapted to the environment. How well a trait or characteristic of an organism fits the environment. It is the environment that determines which traits are the best for adapting, and the organisms with these traits are “selected” to best survive.