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Transcript
Biological Diversity Section 2 Reproduction and Survival 2.1 A Closer Look at Variation Variation is one of the most critical aspects of species survival. Variation may not always be easy to identify. It may be a behavioural tendency or a genetic modification. Variations enable some individuals within a species to survive while others of the same species will perish. Inherited and Non-inherited Characteristics Inherited (heritable) characteristics are traits which are passed on to offspring directly from their parents. These traits are passed on inside the genetic material. Heritable traits include structural and distinguishing characteristics such as eye color, hair type, skin color and earlobes. Non-inherited characteristics are acquired and not necessarily passed on from generation to generation. Ex. Athleticism, artistic ability, leadership qualities are all learned during the early years of life. Discrete and Continuous Variations Discrete variations are differences in characteristics that have a definite form. Individuals within a species have one of two possible expressions of the characteristic. Discrete Variation: Hitchhiker's Thumb Straight thumb Widow’s peak roll tongue Continuous variations are differences in characteristics that have a multitude of variations, such as height, shoe size, or hair color. Variation and the Environment Some variations may be influenced by interactions with the environment. These variations are not inherited. Examples include: Change in the pigmentation of skin color due to sun exposure. Height and weight can be influenced by diet. Now do Check and Reflect p. 29 #1-3, and 6 2.2 Asexual and Sexual Reproduction A. Asexual Reproduction Asexual reproduction involves only one parent. All of the offspring are identical to the parent. There are different types of asexual reproduction: 1. Binary Fission only single-celled organisms reproduce in this way. The cell splits into two cells and each one is identical. Ex. bacteria, amoeba, algae 2. Budding the parent organism produces a bud (a smaller version of itself) which eventually detaches itself from the parent and becomes a self-sufficient individual identical to the parent. Corals reproduces this way, but do not detach themselves Ex. hydra, yeast, coral, sponge 3. Spore Production spores are similar to seeds, but are produced by the division of cells on the parent, not by the union of two cells. One parent may produce many spores, each of which will grow into a new individual, identical to its parent. Ex. fungi, green algae, moulds, ferns Q: How do spores survive unsuitable growing conditions? (p.30) 4. Vegetative Reproduction The reproduction of a plant not involving a seed, including: cuttings, runners, suckers, tubers. Ex. coleus plant, spider plants, strawberries, aspen, potatoes Q: Explain why a cluster of aspen trees turn color at exactly the same time (p.31) Read the infoBIT on p.30 about Parthenogenesis Q: define parthenogenesis In Greek it means: List 5 organisms who may reproduce by parthenogenesis: B. Sexual Reproduction Sexual reproduction usually involves two individual organisms (some plants and animals can self-fertilize). The offspring inherit half of their genetic information from one parent and the other half from the other parent. Sexual reproduction involves specialized gametes (reproductive cells that have only one role - to join with another gamete during reproduction). 1. Sexual Reproduction in Animals Male gametes are called sperm cells and the female gametes are called egg cells or ova. During mating, the sperm cell and the egg cell unite to form a fertilized combination of cells called a zygote. The zygote divides first into two cells and those cells continues to divide over and over(cleavage) resulting in the development of an embryo. The embryo develops into a multicellular organism inside the female (in most mammals) or, outside (in an egg shell) in other animals. Draw the events from fertilization to development of an embryo (p. 32). Weird Fact: In seahorses the female inserts her oviduct into the male’s brood pouch where the eggs are fertilized and develop. In a matter of speaking the male sea horse is pregnant! 2. Sexual Reproduction in Plants Sexual reproduction in plants also involves gametes. Male gametes and female gametes join during fertilization to produce a zygote and then an embryo. Most plants produce both male and female gametes, while some produce only one or the other. Pollen contains the male gametes and is found on the stamen. Ovules contain the female gametes and are found in the pistil. Pollination occurs when pollen is transferred from the anther of the stamen to the stigma of the pistil. Cross-pollination occurs when pollen from one plant is carried to the stigma of another plant by wind, water, animals or insects (bees or butterflies). Cross-fertilization occurs when a grain of the pollen forms a long tube which grows down the style into the ovary. The gametes unite to produce a zygote, which then develops into an embryo. •This usually happens inside a seed which protects the embryo. The seed also provides food (cotyledon) for the embryo as it begins growing when conditions are suitable. •Plants produced as a result of crossfertilization are not identical to either parent plant, but will have a combination of characteristics from both parents. Video Link: Plant Reproduction plant reproduction MonD: Nye: Flowers 3. Organisms that Reproduce both Sexually and Asexually Sponges are organisms that can produce both sexually and asexually. Most plants that produce seeds can also reproduce asexually (cuttings, runners). Advantages and disadvantages of Asexual and Sexual Reproduction Asexual Reproduction Sexual Reproduction ADVANTAGES does not require any specialized cells only need one parent produce many offspring very quickly advantage where the environment doesn't change very much (ex. bacteria). ADVANTAGES • Greater genetic variation within a species • Variation usually helps a species survive when the environment changes. DISADVANTAGES little genetic variation less adaptability to a new or changing environment DISADVANTAGES • Takes a lot of energy • Takes a lot of time • Comparatively smaller populations are produced. Define hermaphrodite (p.32) Give 2 examples. Do Check and Reflect p.36 #1-6, and 11 Do Section Review p.37 # 1,3,5,9,10 Do Flower Lab p.34