Cell Division and Mitosis Overview

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Questions and Answers

What is the primary purpose of mitosis in organisms?

To break down old cells

To produce new cells for growth, repair, and reproduction (correct)

To initiate the process of DNA replication

To increase genetic variation

What occurs to chromosomes just before a cell divides?

They double in number and then dissolve

They become visible and condense (correct)

They disappear completely

They split into multiple fragments

During which stage of mitosis do chromosomes line up along the equator of the cell?

Telophase

Anaphase

Metaphase (correct)

Prophase

What is the role of RNA during the process of DNA function?

To carry the genetic code from DNA for protein synthesis Signup and view all the answers

What happens to DNA during the process of DNA replication?

It unzips and forms two identical DNA molecules Signup and view all the answers

What is a chromatid?

The duplicated form of a chromosome connected at the centromere Signup and view all the answers

How many new cells are produced from one parent cell after mitosis?

Two identical daughter cells Signup and view all the answers

Why is it necessary for a cell to duplicate its chromosomes before undergoing mitosis?

To maintain the same genetic information in daughter cells Signup and view all the answers

What is a key difference between RNA and DNA?

One of the bases in RNA is uracil instead of thymine. Signup and view all the answers

What type of cell results from fertilization?

Zygote Signup and view all the answers

In Meiosis, how many chromosomes do the daughter cells have in humans compared to the parent cell?

Daughter cells have 23 chromosomes, half of parent cells. Signup and view all the answers

During which stage of Meiosis do homologous chromosomes line up along the equator of the cell?

Metaphase I Signup and view all the answers

Which of the following accurately describes a haploid cell?

Has half the total number of chromosomes. Signup and view all the answers

What is the main function of Meiosis in multicellular organisms?

To reduce chromosome number for reproduction. Signup and view all the answers

What is the end product of Mitosis?

Two identical diploid cells. Signup and view all the answers

Which statement is true about the daughter cells produced in Meiosis compared to those produced in Mitosis?

Daughter cells in Meiosis are genetically diverse due to crossing over. Signup and view all the answers

What do isotopes of an element differ in?

Number of neutrons Signup and view all the answers

What is the process of radioactive decay used for in geology?

To estimate when rocks were formed Signup and view all the answers

What does the fossil record primarily provide evidence of?

Continual change and diversity of life Signup and view all the answers

What is the law of superposition in geology?

Older layers are further down while younger layers are closer to the surface Signup and view all the answers

How is half-life defined in the context of radioactive dating?

The time interval for the decay of half of the radioactive atoms Signup and view all the answers

Which of the following is a characteristic of evolution?

Describes changes in populations over generations Signup and view all the answers

What comprises the primary evidence for evolution according to paleontology?

The fossil record Signup and view all the answers

What defines a scientific theory?

An evidence-based explanation for observed facts Signup and view all the answers

What primarily holds a galaxy together?

Gravity Signup and view all the answers

What describes plasma?

Superheated matter forming an ionized gas Signup and view all the answers

What initiated the formation of the Sun?

A shock wave from a nearby supernova Signup and view all the answers

What are the two opposing forces that maintain a star's structure?

Gravity and radiation pressure Signup and view all the answers

What happens to matter within a dying star that can lead to a black hole?

It is compressed into a tiny space Signup and view all the answers

What type of galaxy is the Milky Way classified as?

Spiral galaxy Signup and view all the answers

What is the role of gravity in the formation of stars from nebulae?

To pull gas and dust together Signup and view all the answers

How far is the Sun from the center of the Milky Way galaxy?

25,000 light-years Signup and view all the answers

What does comparative anatomy study?

Similarities and differences in body structures. Signup and view all the answers

What are homologous structures?

Structures that have evolved from a common ancestor. Signup and view all the answers

How have horse limbs adapted over time?

They have lost their toes and walk on a single toe that formed a hoof. Signup and view all the answers

What is the primary characteristic of vestigial organs?

They no longer serve any apparent function. Signup and view all the answers

What evidence supports the theory of evolution according to homologous structures?

They imply that all organisms evolved from a common ancestor with similar structures. Signup and view all the answers

Which of the following is true regarding biogeography?

It studies the distribution of species across continents. Signup and view all the answers

Which animal is not typically found as a herbivore in Australia?

Dingo Signup and view all the answers

Which of the following is considered a homologous structure?

The wing of a bat and the flipper of a seal. Signup and view all the answers

Study Notes

Cell Division

The body needs new cells for growth, repair, and reproduction.
Cell division is the process of producing new cells from old cells.
Mitosis is the type of cell division that makes animals and plants grow and replaces old and damaged cells.
In mitosis, a parent cell divides into two identical daughter cells.
Before a cell divides, it must duplicate all its chromosomes.

Chromosomes

Chromosomes are long, thin strands that condense and become shorter and thicker before cell division.
Each chromosome duplicates into two strands called chromatids, joined at the centromere.

Stages of Mitosis

Stage 1: Two pairs of chromosomes are visible.
Stage 2: Chromosomes are doubled.
Stage 3: Chromosomes line up along the cell's equator.
Stage 4: Chromosomes separate and move to the cell's ends.
Stage 5: Membranes form to produce two new cells.

DNA Replication

DNA replication is the copying of the entire DNA inside a cell before it divides.
It results in two identical DNA molecules, each with an original strand and a new strand.
The parent DNA molecule "unzips" at one end, and complementary bases attach to both strands.

DNA Function

DNA stores information as a series of nucleotides.
A long series of nucleotides forms a gene, which makes one protein.
Proteins are the building blocks of our bodies and control growth and aging.

RNA

RNA is a carrier molecule that copies the DNA code.
It has a different sugar (ribose) and one of the bases is different (U instead of T).
RNA is a single strand of nucleotides.

Meiosis

Meiosis is cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes (sex cells).
Gametes are egg and sperm cells.
Fertilization is the fusion of gametes, creating a zygote.
The zygote divides by mitosis to become an embryo and then a fetus.

Stages of Meiosis

Stage 1: Two pairs of chromosomes are visible.
Stage 2: Chromosomes are doubled and attached at the centromere.
Stage 3: Homologous chromosomes line up along the cell's equator.
Stage 4: One chromosome from each pair moves to the cell's ends.
Stage 5: Chromosomes line up along the equator of each new cell.
Stage 6: Chromosomes separate and move to the ends of each cell.
Stage 7: Membranes form to produce four daughter cells.

Diploid and Haploid Cells

A diploid cell has a full set of chromosomes (two of each chromosome).
A haploid cell has half a set of chromosomes (one of each homologous pair).

Mitosis vs Meiosis

Characteristic	Mitosis	Meiosis
Type of cells produced	Body cells	Sex cells
Function	Growth and repair	Reproduction
Number of stages	1	2
Number of daughter cells	2	4
Number of chromosomes in parent cells (human)	46	46
Number of chromosomes in daughter cells (human)	46	23
Are daughter cells identical to parent cells?	Yes	No

Relative Dating

Sedimentary rocks form in layers called strata.
Fossils are the same age as the rocks they are found in.

Radioactive Dating

Isotopes are atoms of an element with different numbers of neutrons, so they have different atomic masses.
Radioactive elements decay at a known rate.
Scientists measure decayed elements to estimate the age of rocks.

Half-Life

The half-life is the time it takes for half of a radioactive sample to decay.
Examples of radioactive isotopes used for dating fossils include Carbon 14 and Potassium 40.

The Fossil Record

The fossil record is incomplete, as only a tiny fraction of past life has been fossilized.
It provides evidence of the following:
- A vast number of species have evolved from early life forms.
- Existing organisms result from changes in pre-existing species lines.
- New species have formed from pre-existing ones.
- Life forms have developed at slow and uneven rates.
- Environmental conditions have changed over time.
- Organisms have appeared, become abundant, and disappeared.

Evolution

Evolution is the slow change in a population of living things over many generations.
The theory of evolution states that life on Earth has changed over time, with different species developing from a common ancestor.

Scientific Theory

A scientific theory is an evidence-based explanation for a set of observed facts.

Types of Evidence for Evolution

Palaeontology: The fossil record provides direct evidence of evolution, showing continual change and diversification of early life forms.
Law of Superposition: Sedimentary rocks are deposited on top of each other, with older layers lower down.
Comparative Anatomy: Studying similarities and differences in body structures helps determine evolutionary relationships.
- Pentadactyl Limb: Vertebrate limbs (e.g., seal flipper, cat paw, bat wing, human hand) have the same bone structure, showing adaptation to different functions.
- Homologous Structures: Similar structures in different organisms suggest a common ancestor.
- Vestigial Organs: Structures with no current function (e.g., human appendix) suggest they were functional in ancestors.

Biogeography

Continents have characteristic life forms due to isolation and adaptation to specific environments.

The Milky Way

The Milky Way is a spiral galaxy containing billions of stars, dust, and gas.
The Sun is located on one of the spiral arms, about 25,000 light-years from the center.

Gravity

Gravity is the attractive force between any two objects in the universe.
It is a weak force, but becomes significant when masses are incredibly large.

Stars and Gravity

Gravity causes immense pressure within stars, leading to nuclear fusion of hydrogen atoms into helium.
Stellar structure is determined by the balance between inward gravity and outward radiation pressure.

Nebulae

Nebulae are clouds of gas and dust where stars are formed.
The Sun formed from a solar nebula, a cloud of gas and dust.
A supernova explosion likely initiated the collapse of the solar nebula, leading to the formation of the Sun and planets.

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Description

Explore the fascinating process of cell division, focusing on mitosis and the stages involved. This quiz covers the roles of chromosomes and DNA replication, essential for growth and repair in organisms. Test your understanding of how cells reproduce and function in living beings.