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General Outcome #2: Explain the link between reproduction and heredity. Topic 3 – Passing It On Can I identify characteristics that are heritable? Can I identify characteristics that are not heritable? Can I identify characteristics that heredity and environment may both play a role? -these traits are passed down through your genes, the genetic material that makes up your body (much like a map) e.g. You look similar to both your father and mother; you have inherited traits Reproductive Strategies Can I describe types of asexual reproduction? 1. Asexual Reproduction -one parent -offspring are duplicates of the parent; exact copies (clones!!!) -they have the same genetic material, therefore the same characteristics Advantage: There is no need to find a mate. There are fewer genetic mutations. Disadvantage: Since there is little variation between each individual, if one is vulnerable to an environmental change then all will be vulnerable. a) Binary Fission -found normally in one celled organisms (e.g. bacteria, paramecium) http://www.youtube.com/watch?v=J6akNYlkehY&NR=1 once the organism reaches a certain size, the organism makes copies of its organelles and nucleus then divides itself in half - -each new cell is identical to the original b) Asexual Spores -found mainly in fungi, such as mushrooms -spores are single-celled, reproductive structures similar to an egg except that it is an exact copy of the parent -spores can be made by the thousands and can survive in almost any type of environment -spores found in the arctic that were thousands of years old easily grew when they were placed in suitable habitat -zoospores are similar to spores except they have flagella (tail-like structures) that move them around (e.g. Chlamydomonas can form zoospores) c) Budding http://www.youtube.com/watch?v=wfbhwq95Duc -occurs in smaller animals such as sea sponges and hydra -as a hydra grows, one of its cells will form a bud (much like a flower’s bud) and start to grow on its own -eventually this will detach and form a copy of the original organism d) Asexual Reproduction with Plants -the growing tips of roots and stems contain areas of rapidly reproducing cells called meristem -when a plant is damaged, these meristem cells can create copies of the damaged cells and the plant continues to grow -by taking a cutting of the meristem, you can grow an exact copy of the plant (a CLONE) -plants can also reproduce by runners or stems that lay along the ground and form roots to create a new plant e.g. strawberry plants -suckering is the process of shoots arising from existing root systems e.g. poplar trees -bulbs, tubers and corms are also forms of asexual reproduction in plants e.g. Potato tubers e.g. Gladiolus corms e.g. Onion bulbs Asexual reproduction that involves a clone being formed from roots, stems or leaves is also known as vegetative reproduction. Can I describe types of sexual reproduction? Can I describe the formation of zygote and embryo in plant and animal reproduction? http://www.youtube.com/watch?v=9GgAbyYDFeg&safety_mode=true&persist_safety_mode=1&safe=active http://www.youtube.com/watch?v=4gOiujoR-5o&safety_mode=true&persist_safety_mode=1&safe=active 2. Sexual Reproduction -two parents -offspring are combinations of the genetic codes of both parents -gametes (egg and sperm) are involved in reproduction -fertilized cell is called a zygote Advantage of Sexual Reproduction: Recombination of genes allows for more variation therefore promoting natural selection. Natural selection has no intentions or senses; it cannot sense what a species “needs.” If a population happens to have the genetic variation that allows some individuals to survive a particular challenge better than others, then those individuals will have more offspring in the next generation, and the population will change. Disadvantage of Sexual Reproduction: A great deal of time and energy is required to find a mate. http://www.youtube.com/wat ch?v=KYp_Xi4AtAQ Forms of Sexual Reproduction Zygospores Some organisms such as moulds can reproduce asexually by spores but they can also form spore like zygospores that contain genetic materials from two different sources. Bacterial Conjugation Genetic material is passed directly from one cell to another but no actual reproduction happens since there is no increase in the number of cells from this process. Sexual Reproduction in Plants Gymnosperms (“naked seeds”) conifers such as spruce, pine and fir do not form flowers produce seeds inside of cones the seeds are not covered with a fruit Angiosperms flowering plants dioicious-male and female parts on separate plants (unisexual) monoicious—male and female parts on one plant produce seeds that are covered by fruit seed is formed when the pollen and the ovule unite during pollination Sexual Reproduction in Animals 1. External Fertilization -in some animals, such as fish and amphibians, fertilization occurs outside the body Advantages Disadvantages female and male do sperm / egg / zygote can not have to be there dry out if water is not at the same time present can produce a large gametes and zygotes number of eggs unprotected so sensitive since the female to pollutants and does not need to temperature change and carry the babies easy prey water may wash sperm and egg away from each other 2. Internal Fertilization -in some animals, such as mammals, birds, and insects, the egg is fertilized inside the body -when the male sperm enters the female, it travels up toward the egg -when the sperm fertilizes the egg, a zygote is formed within the female With internal fertilization, the egg is fertilized INSIDE the body, but does not always STAY inside the body. e.g. Birds use INTERNAL FERTILIZATION but after the zygote forms and the embryo begins to grow inside the mother then a shell will develop and the bird lays the egg. The embryo will finish developing OUTSIDE the mother. Advantages gametes are kept warm and moist greater chance of fertilization occurring sperm / egg / zygote protected within the mother’s body Disadvantages both male and female must be present greater time and energy investment is required Can I describe examples of organisms that reproduce asexually, sexually and those that use both strategies?