1 UNIT A SECTION 2.0 As species reproduce, characteristics are passed from parents to offspring. 2 Topic 2.1 A Closer Look At Variation Textbook Pages 27 29 1
Variation in a species 3 Not all variations are as evident in a species. Scientists may explore which characteristics species pass on from generation to generation, and how these characteristics show up in individuals. Scientists may also examine other factors, such as the role of the environment in variation. #1 Variation contributes to species survival 4 Reproduction ensures that certain characteristics in a species are passed down from generation to generation. How do these characteristics show up in individuals? Does the environment play a role in variation? #2 2
Examples of Characteristics 5 Jack Pines (some can resist drought, some cannot) Magpies (some can fly longer distances than others) Examples of Characteristics 6 Pea Plants (various seed or pod shape, seed, pod or flower colour, plant height) 3
*Heritable Characteristics* 7 Characteristics that are passed on from generation to generation. Example: eye colour, hair type, shape of nose, skin colour. #3 *Non-Heritable Characteristics* 8 Characteristics that are acquired or caused by the environment. Examples: tanned skin, playing an instrument, tattoos, body piercing, ability to solve math problems. #3 4
Variation 9 Variation means change. It helps a species survive by giving it the ability to survive changes in its environment. *Discrete Variation* 10 Refers to characteristics that have a defined form. These characteristics are of either/or form. Example: Earlobes are either attached or not Example: You can roll your tongue or you can t #4 5
*Continuous Variation* 11 Heritable characteristics that have a range of forms. Recall range: from one number to another Example: Height of adult humans (4 5 6 5 ) Example: Foot size Example: Leg length #4 Variation and the environment 12 Variation in organisms may be affected by the environment. Example: A plant in sunlight would be green and bushy, but a plant in low light would be a pale green and spindly. 6
Variation and the environment 13 Variation in organisms may be affected by the environment. Example: Your height can be affected by diet. (North Americans are taller now than in the 1800s because of better nutrition and access to a wide variety of food.) Variation and the environment 14 Variations caused by interactions with the environment are not heritable. If a child of tall parents doesn t receive proper nutrition, he or she will probably not be as tall as his or her parents. #4 7
15 Other examples of variation: Pointed hairline vs. straight hairline Pointed hairline (widow s peak; dominant trait) Straight hairline (recessive trait) 16 Other examples of variation: Hitchhiker s thumb vs. straight thumb Straight thumb (dominant trait) Hitchhiker s thumb (recessive trait) 8
Homework! 17 Textbook Check and Reflect Page 29 # 1 5 Read Topic 2.2 Page 30 33, 35 36 18 Topic 2.2 Asexual and Sexual Reproduction Textbook Pages 30 36 9
Reproduction 19 Reproduction is the process of making new individuals of a species. Involves passing characteristics from one generation to the next. Results can be identical or very different. #5 *Asexual Reproduction* 20 Only involves one parent. All offspring are identical to their parent (exact copies or duplicates). Does not involve combining DNA. Has a very fast growth rate. Example: sunflowers, grasses, roses #6 10
Asexual Reproduction 21 1. Binary Fission Types of Asexual Reproduction 2. Budding 3. Spore Production 4. Vegetative Reproduction #1. *Binary Fission* 22 A cell splits exactly in two, making two identical individuals. This only works with one-celled organisms like bacteria, some algae and some protists. Example: amoebas #6 11
#1. Binary Fission (Continued) 23 #2. *Budding* 24 The parent produces a smaller version of itself (a bud). Often, the outgrowth eventually detaches and becomes a separate organism. Example: hydra (animal) Example: In some cases, the offspring remains attached to the parent, such as in yeast. #6 12
#2. *Budding* (Continued) 25 Similar Ideas 26 Bud: an outgrowth that is a smaller version of its parent and can develop into a new individual. Shoot: Growth that comes out of a tree. Sucker: A plant growing from a root up out of the soil. 13
#3. *Spore Production* 27 Similar to seeds but are produced by the division of cells of the parent, not by the union of two cells. Example: fern (non-flowering plant), many fungi, green algae, some molds, mosses One individual will produce many spores and each spore can develop into a new individual identical to the parent. Spores remain dormant (sleeping) during unsuitable growing conditions and produce new plants when conditions improve. #6 Fern Spores 28 14
#4. *Vegetative Reproduction* 29 Reproduction of a plant that does not involve the formation of a seed It is caused by environmental or physiological factors to produce a structure that will result in new copies of the parent plant. #6 Examples of Vegetative Reproduction 30 Runners (that reproduce), such as in strawberries Suckers, such as in aspen trees 15
Examples of Vegetative Reproduction 31 Tubers, such as for tulips Cuttings of plants Examples of Vegetative Reproduction 32 Shoots, such as on potatoes Bulbs, such as in daffodils 16
Remember: 33 Asexual reproduction involves being made by the division of cells of the PARENT, and NOT a union of two cells. Asexual Reproduction (2:16) 34 17
*Sexual Reproduction* 35 With fertilization Usually involves two individuals (parents). Involves the exchange of genetic material between two individuals resulting in offspring that are genetically different from the parents. Example: most animal species and flowering plants reproduce sexually #7 *Gametes* 36 Sexual reproduction relies on the union of two specialized sex cells called gametes. Male sex cells (gametes) are called sperm. Female sex cells (gametes) are called eggs or ova. #8 18
*Fertilization* 37 Fertilization is the joining of a sperm cell and an egg cell. #8 *Zygote* 38 When the sex cells (male and female gametes) unite with one another (fertilization), they form a fertilized cell called a zygote. A zygote is: a fertilized cell the first cell of a new individual #8 19
*Cleavage* 39 The cell created by the joining of the two gametes is known as a zygote. The zygote is the first cell of a new individual. The zygote then divides into two cells, then into four, then 8, and so on. The process of these cell divisions is known as cleavage. #8 *Embryo* 40 As cell division continues, a new multicellular life form develops, known as an embryo. An embryo is: A multicellular undeveloped organism in its beginning stages not identical to either parent Some embryos form inside the female parent (i.e. humans), and some form outside (i.e. birds). #8 20
Sexual Reproduction in Animals 41 Sexual Reproduction (2:09) 42 21
Sexual Reproduction in Plants 43 Plants can produce male and female gametes, or just female gametes. 44 Female Flower Parts Involved in Reproduction stigma ovary ovule style The stigma, style, ovary and ovule make up the PISTIL. This is the female part of the plant. #9 22
45 Male Flower Parts Involved in Reproduction anther filament The filament and anther make up the STAMEN. This is the male part of the plant. #9 Flower Parts Involved in Reproduction 46 stigma style anther ovary ovule filament sepal petal receptacle #9 23
*Pollen* 47 Fine yellow powder on the anthers Contains the male gametes and is found in the stamen. anther 48 *Ovules* Contain the female gametes and are found in the pistil. 24
*Pollination* 49 Pollination occurs when pollen from the anther is transferred to the stigma. #10 *Cross-pollination* 50 Cross-pollination occurs when the pollen from the anther of one plant is carried to the stigma of another, by wind, water or animal (i.e. bees). #10 25
*Cross-fertilization* 51 Cross-fertilization occurs when a grain of pollen produces a long tube that eventually grows down the style into the ovary that contains the ovules. The joining of a gamete from a pollen grain and a gamete from an ovule form a zygote. Unlike asexual reproduction, plants will have some characteristics from both parents. #10 Seeds 52 In most plants, the embryo is produced inside a seed. The seed acts as protection and stores food for the embryo to use when it begins to grow into a new individual. The embryo can stay dormant in the seed, while waiting for suitable growing conditions. #10 26
53 Summary: Asexual VS. Sexual Reproduction Asexual Reproduction 54 Advantages can produce lots of individuals very quickly because it doesn t require any specialized cells or a way of bringing gametes together Low energy cost Disadvantages Only happens in favourable conditions Entire population can die if conditions change because offspring is identical to parents 27
Sexual Reproduction 55 Advantages Lots of variation to help survive environmental change Disadvantages Takes a lot of energy Fewer offspring are produced at one time 56 Note: Some organisms can reproduce asexually or sexually. Example: Plants can produce sexually (seeds) or asexually (cuttings). First generation jellyfish reproduce asexually. And second generation jellyfish reproduce sexually. Aphids can produce sexually in the fall (possibly due to sun light and temperature changes), but in the summer females reproduce asexually, essentially cloning themselves to produce more females. Spider plants can produce mini spiders (asexual) or sexually with flowers. 28
Homework! 57 Textbook Check and Reflect Page 36 # 1 8 Section 2.0 Review Handout 29