Now that our DQB is complete, we still have some wonderings about fertilization, gestational periods, and chromosomes...so through some articles, we narrowed down some answers to our questions. We're also thinking about data collection and how it can also bring new insight into our culture of "figuring it out." We're closing the year on a high note here in 6th grade!
We graphed the relationships between three variables (animals, gestational period length, and total number of chromosomes in a fertilized egg) looking for patterns. We're not really sure about everything we see...it's leading to more questions! We've got a genetics guest speaker coming in Friday to help answer our questions!
We finished our final models to answer our Driving Question: How do eggs become chickens (or other living things)? Students were really thoughtful at using their "Gotta have it checklists" and came up with the following lists that all models shared in common after each group presented (in no particular order):
1. Blood’s Role in Cell Development
2. Food, Water, and Nutrient Molecules Entering Cells
3. Chick Developing Over Time
4. Cells Growing
5. Cells Multiplying (Mitosis)
7. Stages of a Living Organism’s Development
I am so proud of students and their hard work in figuring out this phenomenon!
Now that we've figured out so much about how an egg can develop into a chicken, we're hitting the ground running putting all the pieces together! Looking back at our initial models, students were dumbfounded at how their thinking has changed!
We built out checklists today to include what science concepts should be in our models, and are using these lists to guide us through our final model development!
Day 1 Model Development
Day 2 Model Development
Part way through Day 2 we finished our models and began offering constructive feedback to other groups!
So if cells need to grow and copy what's on the insides before they can actually split into two new cells (regardless of whether they're reproducing offspring or growing/repairing), they need something to do that...and we're thinking that the stuff they need to grow is what's in blood (food, nutrients, and water).
So using our good 'ol red onion cells, we exposed the cells to both water and saltwater (think nutrients, folks) and we uncovered the following: that the cell grows in size and shrinks in size. This must mean that stuff enters and leaves the cell and the only possibly way it can do so is through the cell membrane/cell wall.
Since cell membranes and cell walls are porous/permeable, we're thinking that this is how the dissolved food, water, and nutrients in blood (which is pumped everywhere in our bodies) gets into cells to help them grow bigger, copy what needs copying, and split. In order to do this, the "stuff" that enters the cell must undergo a chemical reaction (as cell parts don't look exactly like the "stuff" that goes into a cell) and releases gas (waste). We're thinking this is how new cells are made!
We've done so much figuring out that it makes sense to put all the pieces together to explain how on earth and egg can become a chicken!
We certainly know that cells are what is the foundation of life. We've figured out the following so far:
1. Single-celled organisms grow, copy their insides, and then split...to form new single-celled organisms. This is also knows as asexual reproduction!
2. Multi-cellular organisms' cells grow, copy their insides, and then split...JUST LIKE SINGLE CELLED ORGANISMS. Except, they don't do this to reproduce. They do it to either repair lost or damaged cells (like when we get a scrap or break a bone) or to grow new cells (like when we're going through adolescence or a root grows deeper into the soil).
This all made us wonder HOW the cell actually grows...like what does it consume to get bigger before it splits? And we immediately thought FOOD! So we decided to isolate some cells (yeast was a natural choice), and give them access to what we know visits cells (what's in blood). This means we exposed yeast to water, sugar (food) and salt.
Through out set-up, we figured out the following:
1. Yeast cells consume food and grow and then split (evidence was the higher amount of beige-water in the flask).
2. When they eat, they produce a gas that filled up the balloon (we put this there to make sure nothing got in).
This helped us put these pieces together:
Old cells + food = new cells + gas (waste)
We're kinda figuring that this might happen across species because we know we eat, grow, and produce waste, too. We're thinking this all connects to the chicken growing inside the egg, too. But how on earth does stuff that a cell needs, like water, food, and nutrients actually get into the cell?
We really wanted to see what was going on with the germinal disc of the chicken to know more about how it gets SO MANY cells by the time it hatches; however, it just wasn't possible due to the nature of the chicken's egg shell. But since a zebrafish (related phenomenon) can be compared to a chicken (we have seen them develop fairly similarly despite being fish and birds).
Over the course of three videos, we saw some interesting things:
1. All the fish seem to start as a single cell.
2. Each of those cells seems to grow and then split into two.
3. Each of the fish ends up with so many cells, we couldn't even keep track of the "splitting," which we mathematically saw as this unique doubling pattern--1 cell becomes 2 cells, 2 cells becomes 4 cells, 4 cells become 8 cells, and so forth.
4. There was something else in the egg with the egg, which we are thinking is the yolk and white, like the chicken.
This is all making us think that no matter the organism, there is some type of food molecules for the cells to consume. But is this true for every organism? Even those that don't develop in an egg? Is this how we make new cells ourselves, especially since we've been known to lose some (like when we scrap ourselves) or even when we grow taller (like in adolescence)?
We're starting to see lots of patterns emerge...
Bacteria, which are living things, are made of cells, too.
The food that they move in, is not (yogurt). We're starting to see that things that aren't living aren't made of cells, and we're classifying these things don't eat, move, reproduce, make waste, etc. This is all getting us back to the egg and the chicken...
If the egg white and egg yolk are not made of cells, and instead of made of food molecules, and they are consumed by the chicken which becomes made of many cells by the time it hatches, where do all the cells come from in the chicken before it hatches?!?!
Is that little spot (germinal disc) the start of this all??? We've been wondering about this for some time now!
Yes, they certainly are! We looked at an onion under the microscope to figure this out, and we're turning to bacteria next (another living thing). We're starting to see some patterns here between both this singular and multicellular organisms and wondering how we can put these ideas together to figure out JUST HOW the chicken develops in the egg!
Knowing that other parts of chickens develop after the presence of blood near the germinal disc, we began wondering if other parts of chickens (or even other living things that develop similarly to chickens) are made of cells, too.
We looked at chicken skin, mammal heart, human blood, human skin, and human cheeks.
The underlying pattern: all these things are made of cells.
While the cells may differ in shape or connectedness, we recognize that they all contain similar structures like nuclei (with the exception of human blood), cytoplasm and cell membranes, and are all smaller than one millimeter.
We're starting to think that cells are playing an important role in how the chick (or other living things develop) since we see cells early on and later in their development inside the egg.
We're also wondering if all living things (plants included) contain cells, and if non-living things do, too. How will we figure this out?!?!