This is the first slide of the LabLearner CELL on Human Prenatal Development. From conception, we will emphasize the life development process, highlighting key stages from a single fertilized cell (a gamete) to a fully developed baby. This CELL will guide students through understanding how life forms, develops, and grows at the cellular level.

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This slide introduces three types of cell division, but in this Investigation, we will focus on binary fission and mitosis. We will return to this slide later when we study meiosis, which is important for reproduction.

Left Section: Asexual Cell Division

• Binary Fission (Bacteria & Single-Celled Organisms):

  • Simple cell division used by bacteria and some other organisms.
  • One cell splits into two genetically identical cells.
  • No nucleus, so DNA is copied and then separated directly.

• Mitosis (Multicellular Organisms):

  • Occurs in plants, animals, and fungi for growth and repair.
  • One cell divides to form two genetically identical cells.
  • Maintains the number of chromosomes (e.g., human cells keep 46 chromosomes).

Right Section: Sexual Cell Division (Meiosis – Future Investigation)

• Meiosis is shown for comparison but will be studied later in Investigation 2.
• Unlike mitosis, meiosis creates four genetically unique cells instead of two identical ones.
• Meiosis is important for producing sperm and egg cells.

Bottom Section: Summary of Results

• Binary Fission → 2 genetically identical cells.
• Mitosis → 2 genetically identical cells.
• Meiosis (later study) → 4 genetically distinct cells.

Discussion Questions:

Question: What type of organisms use binary fission?
Answer: Bacteria and some single-celled organisms.

Question: What is the main purpose of mitosis?
Answer: Growth, repair, and replacing old or damaged cells in multicellular organisms.

Question: Why does mitosis create genetically identical cells?
Answer: It ensures that each new cell has the same DNA as the original, so all body cells function correctly.

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Asexual reproduction is a way for some organisms to reproduce without needing a mate. This allows them to multiply quickly.

• Asexual reproduction happens in single-cell organisms like bacteria and fungi.
• Some plants and animals can also reproduce this way in certain conditions.
• The process of binary fission is an example of asexual reproduction.

What is Binary Fission?

• Binary fission is how bacteria reproduce.
• One cell copies its DNA and divides into two identical cells.
• The cycle repeats rapidly, leading to fast population growth.

Advantages and Disadvantages

• Advantages of Asexual Reproduction:
  • Fast reproduction – a single bacterium can divide in minutes.
  • No need for a mate – useful for survival in isolated environments.
• Disadvantages of Asexual Reproduction:
  • Minimal genetic variation – all offspring are identical.
  • Less adaptability – if the environment changes, the whole population is at risk.

Examples of Asexual Reproduction

• Mold (left image) – A fungus that spreads through spores and grows rapidly.
• Fungi (middle image) – Some fungi reproduce by making identical copies of themselves.
• Bacteria (right image) – The fastest example of binary fission, allowing bacteria to multiply quickly.

Summary for Students:

• Binary fission is a type of asexual reproduction.
• It happens quickly, but all offspring are identical.
• Some fungi, mold, and bacteria use this method to reproduce.

Discussion Questions

Question: What is binary fission?
Answer: Binary fission is a type of asexual reproduction where one cell splits into two identical cells.

Question: Why is asexual reproduction both an advantage and a disadvantage?
Answer: It allows rapid reproduction but limits genetic diversity, making organisms less adaptable.

Question: How does binary fission help bacteria survive?
Answer: It allows bacteria to multiply quickly, helping them spread and colonize new environments.

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This slide explains how cells divide through mitosis to help the body grow and develop over time.

The left portion of the slide highlights the stages of mitosis:

Interphase: The cell prepares for division by copying its DNA. This is like getting everything ready before splitting into two.

Prophase: The DNA condenses into chromosomes, and structures called spindle fibers begin to form. The nucleus starts breaking down.

Metaphase: The chromosomes line up in the middle of the cell, like players getting into position before a game starts.

Anaphase: The chromosomes are pulled apart to opposite sides of the cell, ensuring each new cell gets the right amount of DNA.

Telophase: Two new nuclei start forming around the separated DNA, and the cell begins to split.

Cytokinesis: The final step! The cell is completely divided into two identical daughter cells, each with 46 chromosomes.

Mitosis is responsible for growth by making more and more cells. This process happens millions of times daily in your body—growth results from billions of cells undergoing mitosis daily, year after year. Your body keeps growing and healing because mitosis is always happening!

Summary for Students:

• • Mitosis is how your body makes new cells.
  • It helps you grow, heal cuts, and replace old cells.
  • Without mitosis, we wouldn’t grow from babies to adults!

Discussion Questions:

Question: Why is mitosis important for growth?
Answer: Mitosis creates new cells, allowing the body to grow and replace old or damaged cells.

Question: What happens to the number of cells in the body as a person grows from a baby to an adult?
Answer: The number of cells increases from about 1.25 trillion in a newborn to around 36 trillion in an adult.

Question: What is the final step of mitosis, and what happens during it?
Answer: Cytokinesis is the final step, where the cell fully splits into two identical daughter cells.

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This slide explains where chromosomes are located inside a cell and how they store DNA, which carries genetic instructions.

The Cell and Nucleus

• Cell (Largest Structure):
  • This is the basic unit of life in all organisms.
  • The cell contains different parts (organelles), each with a special job.
• Nucleus (Zoomed-In View):
  • The nucleus is the control center of the cell.
  • It holds chromosomes, which contain DNA.
  • Every cell in your body (except red blood cells) has a nucleus storing genetic information.

Chromosomes and DNA

• Chromosomes:
  • These are thread-like structures inside the nucleus.
  • Humans have 46 chromosomes in most cells.
  • Chromosomes are made of DNA, which carries genes that determine traits like eye color and height.
• DNA (Zoomed-In View):
  • DNA is a twisted ladder shape called a double helix.
  • It contains the instructions for building and running an organism.
  • Genes, which are segments of DNA, tell the body how to grow and function.
• Key Idea:
• DNA in the chromosomes determines their functions
• This means that the instructions for life are stored in DNA inside chromosomes.

Discussion Questions:

Question: Where are chromosomes found inside a cell?
Answer: In the nucleus.

Question: What is the purpose of DNA in chromosomes?
Answer: DNA carries genetic instructions that determine traits and control how cells function.

Question: Why is DNA important for life?
Answer: It provides the instructions needed for growth, development, and survival.

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This slide introduces karyotypes, which are visual representations of chromosomes inside human cells. Scientists study chromosomes under microscopes to learn about genetic makeup. The image on the left shows a scientist preparing a chromosome sample.

Magnified Chromosomes

• The round picture in the middle is an image of real human chromosomes seen under a microscope.
• Each human has 23 pairs of chromosomes, for a total of 46 chromosomes in most cells.

Karyotype Diagram (right)

What is a Karyotype?

• A karyotype is an organized chart of chromosomes, arranged in pairs.
• Scientists use karyotypes to study genetic traits and identify disorders.

Sex Chromosomes (Circled Section):

• Males (XY): One X chromosome and one Y chromosome.
• Females (XX): Two X chromosomes.
• The father’s sperm determines a baby’s sex by contributing either an X or a Y chromosome. We will discuss this further in Investigation 2.

Summary for Students:

• A karyotype is a chart of all 46 human chromosomes.
• Each cell has 23 pairs of chromosomes.
• Sex chromosomes (XX or XY) determine if someone is male or female.

Discussion Questions:

Question: How many chromosomes do humans have?
Answer: 46 chromosomes (23 pairs).

Question: What is a karyotype used for?
Answer: A karyotype organizes chromosomes to study genetics and detect abnormalities.

Question: How is a baby’s sex determined?
Answer: The father’s sperm contributes an X or Y chromosome, determining if the baby is male (XY) or female (XX).

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This slide shows a complete set of human chromosomes, organized in pairs. This is called a karyotype, which helps scientists study genetics and identify genetic disorders.

23 Chromosome Pairs

• Humans have 23 pairs of chromosomes (46 total).
• Each chromosome pair is numbered from 1 to 22, with the 23rd pair being the sex chromosomes.
• Each pair contains one chromosome from the mother and one from the father.

Sex Chromosomes

• The 23rd chromosome pair determines biological sex:
  • XX = Female
  • XY = Male
• Since the mother can only pass an X chromosome, the father’s sperm determines if the baby will be male or female.

Why Is a Karyotype Important?

• Used to study inherited traits.
• Helps detect genetic disorders.
• Shows how DNA is organized in human cells.

Summary for Students:

• A karyotype is a chart of all 46 human chromosomes.
• Each cell contains 23 chromosome pairs, one from each parent.
• The 23rd pair determines whether a person is male or female.

Discussion Questions

Question: What is a karyotype?
Answer: A chart that organizes all 46 human chromosomes in pairs.

Question: How many pairs of chromosomes do humans have?
Answer: 23 pairs (46 total).

Question: Which chromosome pair determines a person’s sex?
Answer: The 23rd pair – XX for females, XY for males.

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This slide introduces mitosis, the process where one cell divides to form two identical cells. The images show both real microscope images of mitosis and a student lab activity model to help visualize the process.

Phases of Mitosis Under a Microscope (top images)

These are real microscope images showing the different phases of mitosis:

• Prophase: Chromosomes condense, and the nuclear membrane starts breaking down.
• Metaphase: Chromosomes align in the middle of the cell.
• Anaphase: Chromosomes separate and move to opposite sides.
• Telophase: Two new nuclei form as the cell prepares to split.

Lab Activity Overview

• Students will model mitosis using different materials to represent chromosomes and cell structures.
• Each phase of mitosis is shown step by step so students can compare it to the real microscope images above.

Important Concept:

• Mitosis results in two genetically identical cells.
• This is essential for growth, repair, and replacing old cells in the body.

Summary for Students:

• Mitosis has four main phases: prophase, metaphase, anaphase, and telophase.
• Real cells look like the top images under a microscope.
• Students will model mitosis in the lab using materials to better understand how cells divide.

Discussion Questions:

Question: What is mitosis?
Answer: Mitosis is the process where one cell divides to form two identical cells.

Question: Why do cells go through mitosis?
Answer: To help organisms grow, repair damage, and replace old cells.

Question: How does the lab model help us understand mitosis?
Answer: It allows students to see and manipulate chromosome movements, making mitosis easier to visualize.

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This slide shows fetal development through the three trimesters of pregnancy. Students will use this slide throughout the CELL to track and model fetal length and mass at different stages.

Top Section: The Three Trimesters

• The First Trimester (Red) covers weeks 1-12, when major organs begin to form.
• The Second Trimester (Blue) covers weeks 13-26, when the baby grows rapidly and begins to move.
• The Third Trimester (Green) covers weeks 27-40, when the baby gains weight and prepares for birth.

Each trimester shows a pregnant woman’s body changes along with illustrations of the growing fetus.

Bottom Section: Weekly Modeling Activity

• Students will model fetal growth at weeks 7, 14, 21, and 28 using real fetal length and mass data.
• The colored timeline at the bottom represents fetal growth week by week.
• Blue arrows indicate when students will create fetal size and mass models.

Right Side: Survival Chances Outside the Womb

• The red curve shows the percent chance of survival if a baby is born early.
• Before week 22, survival is very low, but after this, survival chances increase rapidly as the fetus continues to develop.

Discussion Questions:

Question: What will students be modeling throughout the CELL?
Answer: Fetal growth, using length and mass data, at weeks 7, 14, 21, and 28.

Question: Why does the baby’s survival chance increase later in pregnancy?
Answer: The organs, especially the lungs, develop more fully, making survival outside the womb more likely.

Question: What is the role of meiosis in fetal development?
Answer: Meiosis creates sperm and egg cells, which combine during fertilization to start a new human life.

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This slide introduces the full CELL lab activity, where students will model a fetus’s growth by tracking its mass and length over time.

Left Section: Fetal Growth Data Table

• The Table provides realistic fetal mass and length measurements from weeks 1 to 36.
• Highlighted weeks (7, 14, 21, 28, 35) are when students will measure and model fetal growth in the lab.
• Students will use this data to create a physical clay model of a fetus’s size at different stages.

Right Section: Lab Setup

• Students will use scales, rulers, and modeling materials to replicate the approximate mass and length of a fetus at different points in development.
• The triple-beam balance on the bench represents how students will measure the mass of their models as they track fetal growth. Some labs may use a digital scale for this function.
• Hands-on learning: This lab helps students visualize how much a fetus grows over time in a way that numbers alone cannot show.

Bottom Section: Weekly Growth Timeline

• This timeline divides fetal development into trimesters.
• Students will refer to this timeline throughout the CELL to compare their models to real-life growth patterns.

Summary for Students:

• Students will create models of fetal growth at weeks 7, 14, 21, 28, and 35.
• Each model will match real fetal length and mass data.
• This hands-on activity helps students understand how the fetus develops over time.

Discussion Questions:

Question: What will students be modeling in this lab?
Answer: Fetal growth in terms of length and mass at different stages.

Question: Why do we measure both length and mass?
Answer: Because fetal growth includes both getting longer and gaining weight, which helps prepare for birth.

Question: How does this activity help students understand fetal development?
Answer: It provides a visual and physical representation of growth, making it easier to understand than just reading numbers.