Science 9 Biology Notes Package PDF

Science 9 Biology Notes Package I belong to: ____________________________________________________ 1 Cell organelles Review What To Do: Label each cell part to the best of your ability. Consult with your neighbours after you have...

Science 9 Biology Notes Package I belong to: ____________________________________________________ 1 Cell organelles Review What To Do: Label each cell part to the best of your ability. Consult with your neighbours after you have completed all that you recall. 2  Functions Cell Organelle Cell Membrane Cell Wall (plant only) Cytoplasm Mitochondria Chloroplast (plant only) Ribosome Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Golgi Body Vesicles Vacuole Large Central Vacuole (plant only) Nucleus 3  Nuclear Membrane Centrioles (and spindle fibres) Biology:Asexual Reproduction A clone is an identical genetic copy of its parent Many organisms naturally form clones via asexual reproduction Cloning is also used in agriculture and research to copy desired organisms, tissues and genes In asexual reproduction, only one parent is required. Asexually produced offspring, or clones, have identical genetic information to each other and to the parent. Asexually reproducing unicellular organisms reproduce quickly and in large numbers. Knowledge of asexual reproduction enables biotechnologists to clone both organisms and cells. Type of Asexual Reproduction 1) Binary fission - single cell organisms splitting into identical copies 🡪 some kinds of bacteria 🡪 amoeba 2) Budding - areas of multicellular organisms undergo repeated mitosis to form an identical organism. Buds sometimes detach to form a separate organism 🡪 some simple multicellular organisms such as hydras and sponges 🡪 one-celled yeasts 4  3) Fragmentation - part of an organism breaks off due to injury, and the part grows into a clone of the parent 🡪 some plants, such as mosses and liverworts and Eurasian watermilfoil 🡪 some animals, such as some sea stars and corals 4) Spore formation - some bacteria, micro-organisms and fungi can form spores - single cells that can grow into a whole new organism common in fungi some plants and algae 5 6 5) Vegetative reproduction - special cells in plants that develop into structures that form new plants identical to the parent 🡪 very common in most kinds of plants – potatoes, onions, strawberries Human-assisted methods of vegetative reproduction - includes methods such as cuttings and grafts. 🗄♋✆ Cutting method: a plant grower removes a section of stem (or leaf or root) and plants the cutting in a special growing medium. The hormones signal the nuclei in the cells of the cutting to stimulate cell division and growth, which causes some cells to develop into root tissue 🗄♌✆ Grafting method: In grafting, stems called scions are attached to the rooted stock (or “rootstock”) of a similar plant species (Figure 5.28A). Grafting has several advantages. It can help the scion benefit from a more vigorous root system. Grafting can also control the eventual size of the plant. This technique is often used to reproduce apple trees and rose plants. 7 Advantages and Disadvantages of Asexual Reproduction 8 Human Assisted Cloning Humans use all the asexual cloning methods in order to produce desired results with organisms. This is done in several ways: Reproductive cloning - purpose is to produce a genetic duplicate of an existing or dead organism. Making clones of animals involves taking the nucleus from one type of cell and putting it into an egg cell that has had its nucleus removed. As the egg cell divides, its new cells have the DNA from the first type of cell.Steps involved: 9  Therapeutic cloning - purpose is to correct health problems Very important to therapeutic cloning are stem cells. Stem cells that come from human embryos can become any of the 200 types of cells in the human body. Stem cells that come from specific body tissues can become only a few types of body cells. Stem cells can be used to replace cells damaged from injuries or disease such as diabetes, spinal injuries, Parkinson’s disease Very controversial because the best stem cells are from embryos which are destroyed when harvesting cells Quick Check 1. How does binary fission in bacteria differ from binary fission in eukaryotic cells? 2. How does budding in yeast differ from binary fission in amoebas? 3. What is fragmentation? 4. What is plant grafting? 5. What is therapeutic cloning? 10  Biology 9 - Sexual Reproduction In sexual reproduction, a male gamete (sperm cell) must fertilize a female gamete (egg cell). As a result of meiosis and the union of sperm and egg cells, no two individuals will have the same DNA, except identical twins. Many aquatic animals reproduce through external fertilization. Most land animals reproduce through internal fertilization. Following fertilization, the zygote and embryo start to divide by mitosis, and cells will differentiate. In asexual reproduction requires only one parent and can occur wherever that parent is located if conditions are favourable. Sexual reproduction requires two parents who must bring two gametes together for fertilization to occur. To survive, sexually reproducing species must mate with members of their own species. Sexual reproduction is the process that brings these non- identical gametes together to form a new organism. Sexual reproduction has three stages: mating, fertilization, and development. What is the difference between external and internal fertilization? Mating is the means by which gametes (sperm and egg cells) meet in the same place at the same time. Mating enables fertilization to take place. Recall that fertilization is the joining of a haploid sperm cell with a haploid egg cell to form a diploid zygote. When sperm and egg cells join outside of the bodies of the parents, the joining is called external fertilization. This type of fertilization is common with animals that live in water and with plants that live in moist places. External fertilization provides an advantage because very little energy is required to find a mate, and large numbers of offspring are produced at one time. The ability to produce many offspring at once means that some individuals of a population may survive to reproduce in the event of an environmental disaster such as an oil spill that kills off most of the population. Since offspring are usually widely spread out, they do not compete with their parents for food. In addition, there is little chance that the egg from an offspring will be fertilized by the sperm of a parent, so genetic variation will be maintained. There are, however, some disadvantages to external reproduction. Although millions of gametes are released, many will not survive outside the parents’ bodies or meet to result in fertilization. Since zygotes and embryos 11 form outside of the parents’ bodies, they are unprotected and often preyed upon. In addition, since parents do not care for their offspring, few survive to adulthood. When sperm and egg cells join inside the body of the female parent, the joining is called internal fertilization. This type of fertilization is common with birds, mammals, and flowering and cone-forming plants. Internal fertilization provides an advantage because more offspring survive as a result of embryo protection and parental care. However, internal fertilization requires more energy to find a mate. Internal fertilization also results in the production of fewer zygotes compared with external fertilization. Pollination In most plants, internal fertilization is achieved through a process called pollination. Pollination is the transfer of male gametes in structures called pollen (male reproductive part of a plant) grains that carry the sperm cells in a protective case to the ovules, (female plant structures that contain the egg cells). After the pollen lands, a pollen tube forms, which is a structure that delivers the sperm cells to the egg cells. Following fertilization, a zygote grows into an embryo and is nourished by food stored within the seed in which the embryo grows. The seed’s tough outer coating protects the developing embryo. 12 Pollen transport Some flowering plants such as willow, hazelnut, and aspens have flowers that do not have petals. Plants like these release their pollen into the air so that the wind can carry the pollen to the female reproductive parts of other flowers. Plants such as Douglas fir trees do not have flowers. Instead, sperm and egg cells are produced in male and female cones. Such cone-bearing plants are called conifers. Pollen is released from the male cones and is carried by the wind to the female cones. The embryo is protected within seeds in the female cone and completes its development there. Once the egg is fertilized, cell division will occur only if certain conditions are met. There must be enough nutrients for the rapidly dividing embryo. The temperature must be warm enough so that proteins and enzymes will function properly during chemical reactions in the developing embryo. There must be sufficient moisture so that the embryo does not dry out. The embryo must be protected from predators and from other environmental factors such as ultraviolet radiation. Reading Check 1. Egg and sperm cells have substances on their surfaces that aid in species identification. What are these substances? protein 2. What is the method of fertilization for land-dwelling animals? Internal fertilization 3. What is the method of fertilization for water-dwelling animals? External fertilization 4. What is pollination? Transfer of male gametes (pollen) to the female gametes (ovules) 5. What can be found inside a seed? Food and a protective covering and an embryo 13 How does the embryo develop? Embryonic development takes place during the first eight weeks after fertilization. During this time, the embryo develops. Its cells divide constantly, and tissues and organs form. During the first week, the single fertilized cell, the zygote, develops into a mass of many cells. This mass of cells then hollows out and is called a blastula. The cells of the blastula are embryonic stem cells. All tissues and organs will develop from these cells. During the second week, the blastula cells become organized into three distinct layers of cells. The outer layer is called the ectoderm. The middle layer is called the mesoderm. The inner layer is called the endoderm. The illustration on the next page shows which organs and body structures are formed from the cells of these layers. The development of organs and body structures from these cell layers is called differentiation. 14 What happens during fetal development? After the first eight weeks of development, the embryo is called a fetus. During fetal development, the organs and parts of the body continue to develop. The body adds a great deal of mass. At birth, the human baby is made up of trillions of cells. The table below summarizes some key events in fetal development. What are assisted reproductive technologies? In some cases, the male or female in a couple (or both) may be infertile—unable to have a child. Assisted reproductive technologies are methods that are used to help infertile couples have a child. Most of these methods include removing egg cells from a woman’s body, fertilizing them, and then placing one or more of the embryos in her uterus. What types of assisted reproductive technologies are there? Type of technology How it works artificial insemination (AI) Sperm are collected from the male and then injected into the female. in vitro fertilization (IVF) A woman’s egg cell is placed in a petri dish, and then sperm are injected into the dish so that one sperm cell may fertilize the egg. gamete intrafallopian transfer A woman’s egg cell is mixed with sperm, and then the (GIFT) mixture is injected into the woman’s fallopian tubes. This way, an egg may be fertilized inside the woman’s body. intracytoplasmic sperm injection A single sperm cell is injected into an egg cell. The (ICSI) fertilized egg is then inserted into the woman’s uterus 15 Reading Check 1. What is assisted reproductive technology? 2. What is artificial insemination? 3. What is in vitro fertilization? 4. How does the success rate of in vitro fertilization change as the age of the woman increases? 5. What is the difference between gamete intrafallopian transfer and in vitro fertilization? How does society respond to these technologies? Reproductive technologies have helped many couples have a child. However, these methods also raise questions. For instance: What to do with unused embryos: Not all the embryos that result from these methods are used. What should be done with the unused embryos? Some people want to use them for research purposes. For example, the embryos are a source of stem cells that could be used to help cure diseases or regrow impaired or lost organs. Other people think that it is wrong to use the embryos this way. Unknown donors: Sperm used in AI are often donated by strangers. Does a child of an AI method have the right to know the identity of his or her biological father? Surrogate mothers: Sometimes an infertile couple contracts another woman to carry a baby for them. Using AI or IVF, one or both gametes may be provided by the contracting couple. What if the surrogate mother decides she wants to break the contract and keep the baby? Questions such as these do not have easy answers. 16  Biology: Cell Division - Mitosis Prescribed Learning Outcomes for Lesson: Draw a diagram of the sequential mitotic process -phases: interphase, prophase, metaphase, anaphase, telophase, cytokinesis -labels: nuclear membrane, (homologous) chromosomes, (sister) chromatids, centromeres, B.1 spindle fibres, centrioles Recall: The cell cycle (the life progression of most cells) undergoes 3 stages: interphase, mitosis, cytokinesis. In Interphase, the cell grows, repairs, and replicates its DNA.As the nucleus prepares to divide, the DNA molecules that replicated during interphase join together to form the sister chromatids of a chromosome. The centromere joins the sister chromatids. The two diagrams above are called karyotypes, they are a picture of an organism’s chromosome (coiled DNA) in one of their cells. In this case, these pictures show a human’s karyotype. A human has 23 PAIRS of chromosomes: 22 pairs autosomes, and 1 pair of sex chromosomes. Females have two X chromosomes for their sex chromosomes and males have an X and a Y chromosome. The karyotype on the left is taken BEFORE the DNA has been replicated, and the karyotype on the right has been taken AFTER the DNA has been replciated. Mitosis: During this stage, the nucleus of the cell divides into two equal and identical parts. This division results in two daughter nuclei, each with the same number and kinds of chromosomes as the original cell. Each part has a copy of the DNA. Occasionally, mistakes are made during replication, but the daughter cells are usually identical to the parent. 17 What are the phases of mitosis? There are four phases of mitosis. These phases are prophase, metaphase, anaphase, and telophase (PMAT). After PMAT/mitosis, the third stage of the cell cycle occurs: cytokinesis and the parent cell splits fully into two daughter cells. Cytokinesis: During this stage, the two equal, identical parts of the cell separate. The result of this stage is two identical cells, each with a nucleus and DNA. 18 19  Biology Chapter 6.1: Meiosis The process of meiosis results in the production of special cells called gametes. Gametes have half the number of chromosomes as body cells. Cell division occurs twice in meiosis: once at the end of meiosis I and again at the end of meiosis II. In meiosis I, matching pairs of chromosomes called homologous chromosomes separate. In meiosis II, sister chromatids separate. The process of meiosis shuffles genetic information and results in variation in the gametes. What’s special about Meiosis? Unlike asexual reproduction, which requires only one parent and produces identical offspring, sexual reproduction requires two parents. Sexual reproduction produces offspring that are genetically different from each other, from either parent, and from any other member of their species. Variation, or inherited genetic differences in a species, is called genetic diversity. Genetic diversity is the result of sexual reproduction, which randomly sorts, or shuffles, DNA. Because of the combination of genes received from its parents, an organism may be better equipped to cope with changes in its environment. Therefore, one organism of a species may gain an advantage over another organism of the same species. What is sexual reproduction? In sexual reproduction, genetic information from two parent cells is passed on to an offspring. Female organisms and male organisms make specialized cells called gametes. Gametes from female parents are called eggs. Gametes from male parents are called sperm. In sexual reproduction, the gametes from the two parents combine during a process called fertilization to form a new cell. The new cell is called a zygote. The zygote is the first body cell of a new organism. As the zygote undergoes repeated mitosis and cell division, it matures into an embryo. How do gametes differ from body cells? All human body cells have 46 chromosomes. These chromosomes are arranged into 23 pairs. You receive one member of each pair of chromosomes from your mother. You receive the other member of each pair from your father. When a cell has pairs of chromosomes, it is said to be diploid. Di- means two or double, 20 referring to the two sets—the pairs—of chromosomes. Human body cells are diploid. The diploid number for humans is 46, or 2 x 23 chromosomes. Gamete cells, on the other hand, have only one set of chromosomes, for a total of 23 chromosomes. Gametes are said to be haploid. Humans inherit one set of 23 chromosomes from their female parent and one set of 23 chromosomes from their male parent. 21 How do gametes become haploid? In order for human body cells to remain diploid, gametes must have one half the number of chromosomes—that is, 23. Only haploid gametes with 23 chromosomes can combine during fertilization to form a diploid zygote with 46 chromosomes. Meiosis is the process that ensures that each gamete is haploid. In other words, meiosis produces gametes with one half the number of chromosomes as body cells. The process of randomly dividing 23 pairs of chromosomes in half creates millions of possible combinations of chromosomes. Any of these combinations may be combined with chromosomes from the other parent in any gamete during fertilization. In this way, sexual reproduction and meiosis increase genetic diversity (variety) in a species. What happens during meiosis? Examine the diagram below. During meiosis, each chromosome in a cell is duplicated once and then the cell divides twice. The first division of the cell is called meiosis I. Meiosis I is similar to mitosis, but each pair of chromosomes includes one chromosome from each parent. These matching chromosomes are called homologous chromosomes. Meiosis I starts with a diploid cell and finishes with two diploid cells. Each of the two diploid cells undergoes a second division called meiosis II. Meiosis II starts with two diploid cells and ends with four haploid cells. So the overall process of meiosis starts with one diploid cell and ends with four haploid cells. 22 23 Crossing over Crossing over is an important event that occurs between each chromosome pair in meiosis I. In crossing over, parts of non-sister chromatids “cross over” each other and exchange segments of DNA. Therefore, crossing over creates an infinite number of genetic possibilities for just one gamete and results in variation. Independent assortment In meiosis I, independent assortment occurs where homologous pairs of chromosomes separate at the equator and move toward opposite poles of the cell. For each of the 23 pairs of human chromosomes, there are two possibilities for how a chromosome will eventually sort itself into the daughter cells. There are more than 8 million combinations possible for these 23 pairs in any egg or sperm cell. When fertilization occurs, 70 trillion different zygotes are possible from the combination of one sperm cell and one egg cell! Gamete formation In males, meiosis I occurs and produces two cells. It is immediately followed by meiosis II if there are enough nutrients for cell division. The result is four cells with the cytoplasm and organelles equally divided among them. All four cells may develop into mature sperm. In females, meiosis I occurs and produces two egg cells, but there is an unequal division of the cytoplasm and organelles. Following meiosis II, three of the cells will disintegrate. The remaining one large egg cell retains most of the cytoplasm and is available for fertilization. 24 Quick Check 1. What does the term genetic diversity mean? 2. What is the function of meiosis? 3. (a) What is the haploid number of chromosomes in humans? (b) What is the diploid number of chromosomes in humans? 4. What is another name for a fertilized egg? 5. What are homologous chromosomes? Chromosome Mutations in Meiosis Small mutations in genes may have no effect on an organism or may cause disease. Big changes in the organization of DNA and genes happen when pieces of chromosomes are lost, duplicated, or moved within a chromosome or moved to another chromosome. These changes often occur during meiosis, affecting genes and the proteins made from those genes. Chromosome mutations also occur when cells are exposed to mutagens such as radiation or chemicals. Whole chromosome mutations can occur in meiosis I (when homologous chromosomes fail to separate) or in meiosis II (when sister chromatids fail to separate). The result is that one gamete will have two copies of one chromosome and the other will have no copy of that chromosome. Many chromosome mutations are not passed from one generation to the next because the offspring either fails to develop or does not live to reach reproductive age and adulthood. 25 Diagnosing Genetic Disorders A geneticist can prepare a different type of picture of these individuals, one that shows all of their chromosomes arranged in a particular order. This picture is called a karyotype and is prepared by cutting and pasting chromosomes taken from body cells during mitosis. The homologous chromosomes are identified and paired by size, centromere location, and banding patterns. By analyzing karyotypes, geneticists can determine when a whole chromosome mutation has occurred. Understanding which chromosomes have been affected helps physicians diagnose and treat patients with genetic disorders or syndromes. Individuals with Down syndrome have characteristic facial features and shorter stature and may be prone to developing heart defects and diseases such as Alzheimer’s and leukemia. Ninety-five percent of the cases of Down syndrome are caused by an extra 21st chromosome. 26