Reproduction

1. Reproduction As species reproduce, characteristics are passed from parents to offspring.

2. Key Concepts • Asexual and sexual reproduction • Inheritance

3. Learning outcomes • Distinguish between asexual and sexual reproduction and describe examples of each type of reproduction. • Describe types of variations found within a species and determine whether they are discrete or continuous. • Distinguish between heritable and non-heritable characteristics.

4. Look around at the plants in our classroom • Imagine they are all alive (and that I am not currently in the process of killing the living ones). • What do you notice about them?

5. Different shapes, sizes, colours? • If there were 10 of each kind in the room, it might be easier to notice patterns and similarities among species. • Particular species have particular characteristics.

6. Boston Fern • Large green leaves and no real stem.

7. Coleus Plant • Leaves of many different colours growing out of a central stem.

8. Take a look in the classroom at your species • What characteristics do you see that are common to humans?

9. I wonder… • What process ensures that characteristics in a species are passed down from generation to generation?

10. Reproduction

11. Start Taking Notes Here!! • Through the process of reproduction, characteristics are passed on from one generation of a species to the next. • This may through asexual reproduction (one parent) or sexual reproduction (two parents). • Through sexual reproduction, the resulting cells contain different genetic information than the parent cell(s). • Asexual reproduction always results in the formation of cells with identical genetic information.

12. Therefore… • Sexual reproduction is a way of maintaining genetic diversity in a species or population. • Asexual reproduction allows for fast growth of a population of a population of identical individuals, which benefits species survival in a stable environment. • E.g.

13. Review: How can Humans (or any species) be the same, but also different? • Individual members of a species can also have their own unique versions of certain characteristics… Remember eye colour, hair colour in humans… Or 2 plants of the same species can have dark purple leaves, while another’s is red and yellow.

14. Variation • In this section you will discover how these variations occur, and we’ll consider the ethical implications of whether or not artificially “selecting” for certain characteristics is a good idea for human beings to pursue. • “Designer” babies, animals, plants, food sources.

15. Build-A-Baby?

16. Variation • Review from last section… How does variation contribute to a species survival?

17. A genetically "healthy" population is defined as having a large amount of genetic variability. • With a large amount of genetic variation, natural selection is able to operate by altering the frequency of particular alleles (characteristics) in response to environmental conditions. • In dry conditions, plants that carry genes that are resistant to drought will survive.

18. Not all Variation is obvious • Can see hair/eye colour; coloured bands in the banded snail; different leaf colours. • But what can’t you see? Blood type; some trees (Jack Pines for example) exhibit resistance to drought better than others; some bacteria “super bugs” are resistant to antibiotics; resistance to disease in humans/plants/animals? • Why do some students get chicken pox and some never do? (not vaccines)

19. Scientists study… • Which characteristics are passed along from generation to generation. • How characteristics show up in individuals. • The role of the environment in variation. • Although ancient peoples did not know about modern-day genetics, they did understand that characteristics were passed from parents to offspring. A 6000 year old tablet has been found recording the characteristics of 5 generations of horses.

20. Observing variation in human characteristics • In our class… how many people have “double jointed” thumbs? • Have a thumb that is straight or points backwards (hitchhiker’s thumb)? • Have detached ear lobes? • Have a smooth or pointed hairline?

21. Dominant or Recessive? • A pointed hairline (widow’s peak) is a dominant trait. • Hitchhiker’s thumb is recessive. • Attached earlobes is recessive. • Therefore, we should expect about 75% of us to have the first trait, and only 25% of us to have the other two.

22. Heritable and Non-Heritable Characteristics

23. Heritable Characteristics • Are passed on from generation to generation • E.g. eye colour, hair type, skin colour.

24. Non-Heritable Characteristics • Are known as acquired characteristics; are not passed on to other generations. • Unfortunately, if your mom or dad learned to play the piano, or many languages, or how to sew… you were not born knowing how to do those things. • The ability to play an instrument is an acquired characteristic, as is dyed hair. If you colour your hair red, green, blue, purple, yellow, tan, tangerine, orange, brown, black, white, or striped… your children will not inherit the dyed colour.

25. Inherited Predisposition • Do not confuse the inherited predisposition of musicality, with the ability to play an instrument. • While someone might inherit a musical ability, would they automatically know how to play an instrument they were handed after being raised in a culture where music wasn’t played/after never hearing music?

26. Discrete and Continuous Variation

27. Discrete Variation • The term refers to characteristics that have a defined form. • “either/or” variation • You either have blue eyes, or you do not have blue eyes; you either have blond hair or you do not have blond hair. • Your earlobes are either attached, or they are not.

28. Continuous Variation • Term refers to differences in characteristics that have a range of forms. • Consider height… adult humans come in a range of many different heights; there are many possible variations in height. • Weight (mass) is also a variation that is continuous (although wouldn’t it be great if I could inherit skinny?). • Shortest? Tallest?

31. Variation and the Environment • Some variations in individual organisms result from interactions with the environment.

32. If you take 2 plants of the same species and plant one in a sunny window, and the other in a dark closet, the two plants would soon begin to look very different. • Remember our class discussion about how humans have grown taller over time? This was a combination of a heritable characteristic and environmental interaction.

33. For example, North Americans are generally taller than they were in the 19th century because of better nutrition and access to a wide variety of food. • Variations caused by interactions with the environment are not heritable. An offspring of that plant grown in the closet would not look like its parent unless it was grown in the same conditions. • 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.

34. Is it discrete or continuous? • Activity: Close your eyes and quickly grasp your hands together above your head, interlocking your fingers. Now look to see which thumb is one top, right or left? • Which way feels more natural? • From class data, is there a hand-clasping preference? • Is this an example of a discrete or continuous trait?

35. Check & Reflect • Page 29, 1-6