Science 9 Chapter 1 Section 1 1 Cell

Science 9 - Chapter 1

Section 1. 1 Cell Division

Cell Theory: 3 Main Ideas • All living things are composed of cells • Cells are the basic units of structure and function in living things • All cells are produced from other cells

Why does Cell Division Matter? • In order for you to grow from a single cell (a zygote) to a teenager with trillions of cells, each new cell had to be created from an older cell. • Also, every time you have damaged cells (cut yourself, broken a bone, etc. ) your body had to make new ones. Cell division is crucial for your life!

The Role of Microscopes • Many centuries ago Greek philosophers thought that organisms appeared from nonliving or rotting material, and idea called spontaneous generation (Example: wheat and sweaty clothing were thought to produce mice)

• In 1665 Robert Hooke created and used a simple microscope to observe a piece of cork – noticed it was made up of air-filled sacs that he called cells.

• In 1838, with more advanced microscopes, German biologists Schleiden and Schwaan recognized that all plant and animal cells have a nucleus and other key organelles. They proposed cells as the basic unit of life.

• Finally Rudolf Virchow observed cells and cell division, and determined that all cells come from other cells. • Our understanding of cell theory is dependent on the microscope!

The Cell Cycle • Many cultures around the world see cycles as a key factor in our lives – the seasons, the day, etc. The same is true for cells. • The cell cycle is the process by which the parent cell grows, duplicates itself, and divides to produce new daughter cells. There are 3 main stages: Interphase, Mitosis, and Cytokinesis.

Interphase • The longest phase of the cell cycle. Normal cell functioning and growth. DNA is mostly not tightly coiled (it’s being read). Then, just prior to Mitosis, the chromosomes are each duplicated. By the end of Interphase there are 2 exact copies of every chromosome in the cell.

Mitosis • This is when the nucleus divides. • Mitosis is the process that produces almost all new cells. Each daughter cell produced by mitosis is genetically identical to the parent cell. A different type of cell division is used to produce sex cells. • There are 4 stages…

Stage 1: Prophase • Prophase (Prepare) – The doubled chromosomes condense and shorten and become visible under a microscope. The nuclear envelope (membrane) begins to disappear. The mitotic spindle forms.

Stage 2: Metaphase • Metaphase (Middle) – The doubled chromosomes line up in the middle of the cell on the mitotic spindle. Nuclear envelope is completely gone.

Stage 3: Anaphase • Anaphase (Apart) – The chromosome strands separate and move toward opposite ends of the cell, pulled by the mitotic spindle. The two sets of chromosomes are identical.

Stage 4: Telophase • Telophase (Tear or Two Nuclei) – The separated chromosomes arrive at opposite ends of the cell. Mitotic spindle disappears. • Two new nuclear envelopes form, one around each set of chromosomes. The chromosomes begin to lengthen and become less condensed, no longer visible under microscope.

Telophase

Cytokinesis • The last phase of the cell cycle. This is when the cell divides into two new cells. In animal cells, the cell membrane pinches inward to form two cells. • In plant cells a new cell wall forms between the two new nuclei. After cytokinesis each daughter cell enters Interphase.

Cytokinesis

Work Time • Mitosis Worksheet – Can work with a partner (1 sheet) • Read Section 1. 1 – vocab words from 1. 1 • Then we’ll continue on with notes

Haploid & Diploid • Cells which contain the full set of 2 copies of each chromosome (2 sets of 23 for 46 total in humans) are said to be diploid. – “di” is a prefix that means 2 • Cells that contain only 1 copy of each chromosome (1 set of 23 in humans), are said to be haploid. Sex cells (sperm and egg cells) are an example of haploid cells.

Cell Division & Cancer • A cell’s DNA usually controls the cell cycle so that cells only reproduce as needed, and that cells die when they get old or damaged. • When the part of the DNA responsible for this control is damaged, however, it can lead to uncontrollable cell division, resulting in tumours. This is how cancer works.

Benign & Malignant • There are two types of tumours: – Benign tumours grow quickly and crowd other cells, but they don’t do any other damage. They don’t spread and they’re considered noncancerous. – Malignant tumours grow very quickly, and they invade and damage other tissues and organs. Cells from these tumours can separate and travel through the bloodstream to other parts of the body. They are considered to be cancerous, and are very dangerous.

Causes of Cancer • Sometimes due to errors in replicating the cell’s DNA • Sometimes due to exposure to carcinogens – Preventing cancer by avoiding these carcinogens is easier than treating cancer once you have it!

Questions: • 1. List the 4 stages of Mitosis and describe what happens in each stage. • 2. A female bee has two copies of each of her chromosomes, but the males have only 1 copy of each chromosome. Which of these bees would be called haploid, and which would be called diploid? Male= Female=

Start Up • Only 3 days left! • Hand back marked assignments • Homework check – Get out your Chap 1 vocab list • I’ll come around to check your 1. 1 words • Then we’ll work on the 1. 2 Notes • Remember – quiz Friday (1. 1 -1. 2) – Can bring in: • Chapter 1 vocab list • Chapter 1 notes package

Section 1. 2 Asexual Reproduction

What is Asexual Reproduction? • Asexual reproduction is any type of reproduction that involves only one parent. • All offspring from asexual reproduction are genetically identical to the parent and to each other. These identical offspring are called clones.

Advantages • One advantage of asexual reproduction is that many offspring can be produced very quickly, creating a large population. • When the environment is stable, genetic variability is not very important, so this can be a very successful strategy.

Disadvantages • The main disadvantage is that any factor that negatively affects the parent will also impact all of the offspring in the same way. So a single environmental change or a new drug or disease can wipe out the whole population very easily.

Types of Asexual Reproduction • Binary Fission: Occurs when single-celled organisms (bacteria, amoebas, paramecia, etc) divide into two identical daughter cells that are clones of the parent. Essentially the same as mitosis.

Types of Asexual Reproduction • Budding: A small miniaturized clone forms as a bud off the parent’s body. In hydra and yeast, these buds detach and become separate individuals. In corals, the offspring remain attached, forming a large structure of many individuals.

Types of Asexual Reproduction • Parthenogenesis: A unique process where unfertilized, haploid eggs mature into new individuals. Example: Bees: unfertilized eggs become male drones, but fertilized eggs become female workers and queens. Also occurs in some species of fish, snakes and lizards.

Types of Asexual Reproduction • Spores: Spores are haploid cells that can develop into new organisms. – This is similar to parthenogenesis, except that spores are not unfertilized sex cells, they are simply haploid reproductive cells. No fertilization is possible. • Spores are similar to seeds since they contain and protect the DNA from unfavourable conditions. They can remain dormant until environmental conditions are just right. • Spores are found in many fungi, green algae, some moulds, and non-flowering plants such as ferns.

Types of Asexual Reproduction • Vegetative Reproduction: The asexual production of genetically identical offspring (clones) from the parent plant, without the formation of a seed. Runners, tubers, and rhizomes are all methods of vegetative reproduction.

Types of Asexual Reproduction • Fragmentation: a new genetically identical individual is formed from a piece of the parent organism. Examples: Some worms can grow two new individuals when cut in half, and starfish can regrow a whole body from one piece of an arm.

Homework • Read Section 1. 2 – Add to vocab list • Remember you can bring this list, and your notes package, into the quiz on Friday! • Holiday Homework: Complete Vocab List – Due Jan 6

Types of Asexual Reproduction • Grafting: A piece of a plant is joined with another plant, called the “parent tree” or “root stock. ” The two plants heal together and grow as one plant, but each part maintains its characteristics. Used to grow two types of apple on the same tree, or to produce two types of flower from the same bush.

Types of Asexual Reproduction • Plant Tissue Cultures: plant cells can be placed in a petri dish with nutrients and grow into new individuals. Once they have developed into a seedling, they can be transplanted into soil and then continue to grow normally. This can be used to preserve endangered species of plants, or to clone plants for particular characteristics.

Question • Select 2 methods of asexual reproduction. Use a Venn Diagram to compare and contrast the two methods.

Activity • Microscope Photo Activity – Look for each stage of mitosis, try to guess which is which

Cell Cycle Stages

Which is which?

Which is which?

Homework • Read Section 1. 2 – Add to vocab list • Remember you can bring this list, and your notes package, into the quiz on Friday! • Holiday Homework: Complete Vocab List – Due Jan 6

Start-Up Activity • Matching Activity – Work with a partner or group of 3 – Try to match up each type of asexual reproduction with its description show me when you think you’ve got it • When done, start reading section 1. 3 – Vocab (will be due tomorrow) • We’ll do the quiz once all groups are done – Get out your notes package and your vocab list

Quiz • Can use the following: – Chapter 1 Notes Package – Chapter 1 Vocab list • When Finished: – Read Section 1. 3 – Vocab words – due Jan 6 th • I’ll be checking the whole list on the first day back, for marks!

Section 1. 3 Sexual Reproduction

Sexual Reproduction • Sexual reproduction is the union of two sex cells (also called gametes) to produce a new individual. This means that 2 individuals combine their genetic information to produce offspring that are similar (but not identical) to themselves.

Gametes • The gametes (sex cells) produced by females are called eggs (or ova), while the gametes produced by males are called sperm. When these gametes join, the process is called fertilization.

Making Gametes • Gametes are haploid (contain only 1 set of chromosomes), and they are produced from a diploid cell by a process called meiosis. Meiosis only occurs in the sex organs (testes in males, ovaries in females).

Meiosis • At the beginning of meiosis, the doubled chromosomes pair up, and only 1 of each pair (either from mom or dad) goes to each daughter cell. • Then a second round of cell division takes place, which is very similar to mitosis, and the final result is 4 daughter cells, each with 1 copy of 1 set of chromosomes. This is why you only share 50% of your genes with your mom, and 50% with your dad.

Meiosis

Animals • When two haploid gametes join (fertilization), a single diploid cell is formed, called a zygote. • The zygote has a full set of chromosomes, and is the first cell of the new individual. • The zygote divides many, many times via mitosis, forming a small clump of cells, called the embryo.

Animals • In most mammals, the embryo develops mostly inside the female.

Animals • In most other species of animals, the embryo develops mostly outside the female’s body, in an egg.

Animals • The new individual will have some features of each of the parents, and often some new features not seen in either parent. This offspring is similar, but not identical to, its parents.

Start Up • Get out Chapter 1 notes so we can finish them • Then: Chap 1 -2 Take Home Test Assignment – Start Today, Finish Monday – I’ll Check Vocab Lists while you work

Where do your genes come from? • Video (4: 21) – http: //www. youtube. com/watch? v=-Yg 89 GY 61 DE

Why Does Meiosis Matter? • If the two gametes were each diploid, then the zygote would have 4 of each chromosome, and in the next generation it would have 8, and so on. Meiosis ensures that the number of chromosomes stays the same in each new individual.

Hermaphrodites • Most animals have distinct sexes – each individual is either male or female. • Some animals are hermaphrodites – they can produce both male and female gametes. • Earthworms, snails, and slugs are common examples of hermaphrodites. • These individuals usually mate with other individuals of their species, though in some cases they can also fertilize themselves, usually in times of environmental stress.

Greek Mythology Connection Hermaphroditos was a son of Hermes and Aphrodite, the gods of male and female sexuality. The nymph Salmakis fell in love with Hermaphroditos and prayed to be united with him in one body – both male and female atributes.

Sexual Reproduction in Plants • Sexual reproduction in plants requires some kind of flowers, since flowers are the sexual organs. Some plants produce only male or female gametes, but many produce both types, like a hermaphrodite.

Plants • Pollen contains the male gametes, which is found on the stamen (male part). • Ovules contain the female gametes, and are found in the pistil (female part).

Pollination • Pollination – when pollen is transferred from the anther (part of the stamen) to the stigma (part of the pistil) – this can happen within a single plant (self-pollination), or between two plants (cross-pollination).

Cross Pollination • Cross pollination requires the pollen to be carried from one plant to another by wind, water, or by a pollinator such as an insect, bird, or bat.

Fertilization in Plants • After pollination, fertilization can occur when two gametes join to become a zygote, and then repeated rounds of mitosis turn the zygote into a multi-cellular embryo. The embryo is usually produced inside a protective coating called a seed.

Seeds • The seed protects the embryo and stores food for when the embryo begins to grow. The seed can stay dormant for a long time before germinating (starting to grow) when conditions are right.

Summary • A plant produced from cross-pollination will be similar but not identical to the two parent plants.

Questions These are in your notes: 1. Complete the table to compare Mitosis & Meiosis 2. Make a Venn Diagram to compare male and female gametes in plants 3. List 3 ways pollination can occur

Questions Mitosis Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Meiosis

Questions Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Mitosis Meiosis Almost all cells Occurs only in sex organs (testes and ovaries)

Questions Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Mitosis Meiosis Almost all cells Occurs only in sex organs (testes and ovaries) 2 daughter cells 4 daughter cells

Questions Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Mitosis Meiosis Almost all cells Occurs only in sex organs (testes and ovaries) 2 daughter cells 4 daughter cells Yes, identical No, not identical

Questions Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Mitosis Meiosis Almost all cells Occurs only in sex organs (testes and ovaries) 2 daughter cells 4 daughter cells Yes, identical No, not identical 2 sets (diploid) 1 set (haploid)

Questions Location/types of cells that it occurs in Number of cells produced from one parent cell Daughter cells identical or not? # of sets of chromosomes in daughter cells Type of cells produced Mitosis Meiosis Almost all cells Occurs only in sex organs (testes and ovaries) 2 daughter cells 4 daughter cells Yes, identical No, not identical 2 sets (diploid) 1 set (haploid) Almost all cell types Gametes – eggs and sperm

Questions • Venn Diagram to compare male and female gametes in plants Male -In pollen grains -Found on anthers, part of the stamen -Often need to be carried by a pollinator, or by wind or water Female -haploid -needs to meet with the other gamete to form a zygote -Called ovules -Found in the pistil -Remain in place, where fertilization occurs

Questions • List 3 ways that pollination can occur: – Wind – Water – Pollinator: • Insect (bees, butterflies, moths, etc. ) • Birds (hummingbirds etc. ) • Bats

Advantages and Disadvantages of Sexual Reproduction • Advantages: Sexual reproduction leads to variation in each new individual. The species has a better chance of surviving environmental changes, since some individuals will be better suited to those new conditions.

Advantages and Disadvantages of Sexual Reproduction • Disadvantages: Gametes must be produced (which requires time and energy) and they must meet with gametes of the same species (which requires finding a mate in animals, or making use of wind, water, or pollinators in plants). • Finally the embryo must be protected and provided with nutrients. • This high energy and time requirement means that numbers of offspring are limited.

Best of Both Worlds? • Some species can reproduce both sexually and asexually. Having the option of asexual reproduction allows fast growth, while reproducing sexually increases genetic variation and chances of survival.

Best of Both Worlds? • Many plants can produce seeds sexually, or they can use runners, cuttings, or tubers to reproduce asexually. Some plants can also produce seeds asexually – without fertilization (some grasses, sunflowers, and roses).

Best of Both Worlds? • Some animals can also do this – parthenogenesis allows for haploid individuals to be produced asexually, and diploid individuals to be produced sexually. • Bees and other social insects do this, as well as some fish, snakes, and lizards. Sponges can also reproduce both sexually and asexually.

Questions • Complete the table comparing sexual and asexual reproduction

Answers Asexual Reproduction What kinds of organisms use this method? Offspring genetically identical to parents? Advantages Disadvantages Sexual Reproduction

Answers Asexual Reproduction What kinds of organisms use this method? Offspring genetically identical to parents? Advantages Disadvantages Sexual Reproduction Bacteria, single-celled organisms, yeast, hydra, fungi, many plants Most animals and all flowering plants. including ferns, some animals including bees, some fish, some snakes, some lizards, and sponges

Answers Asexual Reproduction What kinds of organisms use this method? Sexual Reproduction Bacteria, single-celled organisms, yeast, hydra, fungi, many plants Most animals and all flowering plants. including ferns, some animals including bees, some fish, some snakes, some lizards, and sponges Offspring genetically identical to parents? Advantages Disadvantages Yes, identical No, not identical

Answers Asexual Reproduction What kinds of organisms use this method? Sexual Reproduction Bacteria, single-celled organisms, yeast, hydra, fungi, many plants Most animals and all flowering plants. including ferns, some animals including bees, some fish, some snakes, some lizards, and sponges Offspring genetically identical to parents? Yes, identical No, not identical Can produce many offspring very quickly and with little investment. Great in stable environmental conditions. Since offspring are not identical, they are better able to deal with variable environmental conditions. Won’t be wiped out by a single change in the environment Advantages Disadvantages

Answers Asexual Reproduction What kinds of organisms use this method? Sexual Reproduction Bacteria, single-celled organisms, yeast, hydra, fungi, many plants Most animals and all flowering plants. including ferns, some animals including bees, some fish, some snakes, some lizards, and sponges Offspring genetically identical to parents? Yes, identical No, not identical Advantages Can produce many offspring very quickly and with little investment. Great in stable environmental conditions. Disadvantages Vulnerable to environmental change. Can be wiped out by a single change to the environment. Since offspring are not identical, they are better able to deal with variable environmental conditions. Won’t be wiped out by a single change in the environment Offspring numbers are limited because of the time and energy required to produce gametes, ensure they meet, and protect and provide for the embryo.

Take Home Test • Instead of a Test: a take home test – Looks like a test – Can use your notes & the textbook – Can work on it in class and at home – Can choose to do it with a partner or alone • Due Monday at the End of Class – Will have a few minutes on Monday to finish