1. GCE BIOLOGY BY2 Reproductive Strategies GCE BIOLOGY BY2 Reproductive Strategies

2. GCE BIOLOGY BY2 Reproductive Strategies 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 20 Which Came First? ChickenEgg The Chicken?The Egg? Place your vote by clicking the ‘Chicken’ or ‘Egg’ button Be prepared to justify your choice Which came first? OR

3. GCE BIOLOGY BY2 Reproductive Strategies Reproduction What type of reproduction does this animation represent? Hint: Mitosis is involved. Identical offspring to the parent is produced. Simple unicellular organism Next: What type of reproduction?

4. GCE BIOLOGY BY2 Reproductive Strategies 2 Types of Reproduction: 1)Asexual reproduction - produces individuals that are genetically identical -uses mitosis 2)Sexual reproduction - produces offspring that are genetically different -uses meiosis

5. GCE BIOLOGY BY2 Reproductive Strategies Sexual Occurs when unicellular organisms, such as amoeba reproduce Produces offspring showing variation from the parent Only involves mitosis Involves the production of haploid gametes (n) (sex cells with one copy of each of the parents’ chromosomes) What Type of Reproduction? Drag the corresponding numbers to the appropriate circle to determine if the statement relates to sexual or asexual reproduction: Asexual 1 2 3 4 1 2 3 4

6. GCE BIOLOGY BY2 Reproductive Strategies Asexual vs. Sexual AsexualSexual Produces individuals that are genetically identical (clones) Produces offspring that are genetically different No need for a partnerRequires a partner (usually) No gametes requiredRequires haploid gametes to fuse No increase in variation (except by mutation) Increases variation Does not lead to adaptationAllows a species to adapt to environment change though natural selection A disease could affect all organisms since genetically the same Variation allows some organisms to survive a disease Can be much faster and so allows colonization of an area quickly if it is well suited to that environment Less rapid Produces a stage in the lifecycle that is more resistant to adverse conditions (seeds, eggs)

7. GCE BIOLOGY BY2 Reproductive Strategies Outline of Mitosis Diploid parental cell (2n) Duplication of a Chromosome is Followed by nuclear division Diploid daughter cells (2n) Next: Outline of meiosis

8. GCE BIOLOGY BY2 Reproductive Strategies Outline of Meiosis maternal chromosome paternal chromosome Diploid parent cell (2n) Each chromosome duplicates to form two Pairs of chromatids 2 chromatids centromere Meiosis I Meiosis II Haploid gametes (n) Next: Comparison of mitosis and meiosis

9. GCE BIOLOGY BY2 Reproductive Strategies Comparison of Mitosis and Meiosis Diploid parental cell 2n First division Diploid daughter cells 2n Haploid gametes nnnn 1st meiotic division (meiosis I) 2nd meiotic division (meiosis I)

10. GCE BIOLOGY BY2 Reproductive Strategies Asexual: Examples Cuttings Budding Binary fission Tubers Runners Bulbs

11. GCE BIOLOGY BY2 Reproductive Strategies The Human Life Cycle 2n meiosis mitosis 2n zygote 2n fertilisation n n This is an example of a diploid life cycle

12. GCE BIOLOGY BY2 Reproductive Strategies The Human Life Cycle Drag the labels provided to create the Human life cycle Human fertilisation sex organs zygote gametes adult

13. GCE BIOLOGY BY2 Reproductive Strategies Gametes (sex cells) Males and females usually produce different sized gametes Male gamete is usually small and motile Female gamete is usually large, sedentary and stores food

14. GCE BIOLOGY BY2 Reproductive Strategies Fertilisation the fusion of the haploid sperm and haploid egg to produce a diploid zygote humancoral

15. GCE BIOLOGY BY2 Reproductive Strategies External External – most aquatic organisms – Lots of gametes wasted as they don’t end up meeting (carried by currents..) – Mating ritual/coupling increases chances as male releases sperm directly after the female releases eggs (ex: amphibians)

16. GCE BIOLOGY BY2 Reproductive Strategies Internal Internal- adaptation for land organisms – Means less gamete wastage – Needs some kind of intromittent organ to get sperm into female body (i.e. penis- can enter female reproductive organ)

17. GCE BIOLOGY BY2 Reproductive Strategies External v. Internal ExternalInternal More gametes wastedLess gametes wasted Water needed for male gameteWater not needed for male gamete More eggs and sperm needed to ensure survival of enough offspring Fewer eggs needed as mother protects them/carries them Specialised organ needed to deposit sperm in female Egg exposed more to environmentEggs can get a protective covering after fertilization -or embryo develops in mother Offspring more developed when born increasing chance of survival

18. GCE BIOLOGY BY2 Reproductive Strategies The Life Cycle of a Fish Fish eggs spawning Larval fish fry juvenile adult

19. GCE BIOLOGY BY2 Reproductive Strategies Fish External fertilization Many eggs and sperm required as a great deal are wasted (never come into contact due to predation, water currents..) Eggs exposed to environment/predation shark seahorse

20. GCE BIOLOGY BY2 Reproductive Strategies Gradual Adaptation to Land Amphibians still require water for fertilization External fertilization tadpole has gills and must live in water Reptiles internal fertilization amniote egg eggs protected in a nest external shell to eggs for protection

21. GCE BIOLOGY BY2 Reproductive Strategies Birds Internal fertilzation Eggs incubated by parent in a nest Mammals Embryo nourished by placenta in uterus Young born relatively advanced

22. GCE BIOLOGY BY2 Reproductive Strategies Metamorphosis: Frog Drag the images provided to create the life cycle of a frog The Frog Lifecycle animation

23. GCE BIOLOGY BY2 Reproductive Strategies Amniote Egg in reptiles and birds adaptation to life on land has a fluid filled cavity and a protective shell which encloses the embryo within the yolk sac birds incubate eggs and the embryo completes its development outside the mother’s body Mother protects young

24. GCE BIOLOGY BY2 Reproductive Strategies In mammals the young are retained for a considerable time in the mother’s womb or uterus embryo is nourished from the mother’s blood supply via the placenta young are born in a relatively advanced state of development There is a relationship between the degree of parental care and the number of offspring produced

25. GCE BIOLOGY BY2 Reproductive Strategies Fertilisation Human Fish Compare fertilisation in a fish and humans A strong possibility that many of the eggs will not encounter sperm A lot of waste with both sexes producing a large number of gametes Fertilisation happens inside the body An intromittent organ required to transfer sperm into the female’s body

26. GCE BIOLOGY BY2 Reproductive Strategies Plant Reproduction using water sporophyte spores gametophyte mitosisfertilisation zygote male gamete female gamete diploid haploid mitosis

27. GCE BIOLOGY BY2 Reproductive Strategies Plants also show adaptations to land Some simple plants (algae, seaweeds) require water for fertilization Ferns and mosses live on land but in damp areas and also require water for fertilization as they have motile male gametes Flowering plants are well adapted for life on land in terms of their morphology and reproduction

28. GCE BIOLOGY BY2 Reproductive Strategies Flowering plants reproductive strategies for land colonisation: – relationship with animals, particularly insects, for pollination and seed dispersal – male gamete inside a pollen grain with a protective coat to prevent drying – water not required for male gamete to move to female gamete (uses a pollen tube that grows down to ovule) – eggs (ovules)are protected inside an ovary

29. GCE BIOLOGY BY2 Reproductive Strategies Flowering plants – seed have a food store which enables the embryo plant to develop until leaves are produced above ground – the seed also has a resistant coat that enables it to withstand adverse conditions – rapid germination of seeds

30. GCE BIOLOGY BY2 Reproductive Strategies Reproduction Task: Compare the life cycle shown below.

31. GCE BIOLOGY BY2 Reproductive Strategies Insects Are abundant, extremely diverse, successful and widespread group Mainly terrestrial (some may have aquatic larvae ex: mosquitoes) Have internal fertilization but don’t protect eggs Eggs are laid upon or inside of a food source

32. GCE BIOLOGY BY2 Reproductive Strategies Metamorphosis zygote of insects develops into an intermediate form, (either a nymph or a larva) before becoming an adult. Nymphs resemble the adult Larvae are different from the adult and the larval stage is followed by the pupal stage

33. GCE BIOLOGY BY2 Reproductive Strategies The Insect Life Cycle Many insects change form during their lifetime - this is called metamorphosis. They do this in one of two ways: b) incomplete metamorphosis - nymphs resemble the adult and progress through a series of moults to become the adult a)complete metamorphosis- larvae are different from the adult and the larval stage is followed by the pupal stage (when it undergoes considerable change) Most insects have this type Click on the images above for a larger version of the life cycles Next: The fly life cycle

34. GCE BIOLOGY BY2 Reproductive Strategies The Insect Life Cycle The Butterfly eggspupa larva butterfly (adult) NextBack Butterfly life cycle video

35. GCE BIOLOGY BY2 Reproductive Strategies The Insect Life Cycle The locust eggs nymph (showing rudiment of wings) locust (adult) instars (showing first wings) Back

36. GCE BIOLOGY BY2 Reproductive Strategies The Insect Life Cycle The Fly Eggs 1st larval stage 2nd larval stage 3rd larval stage Pupa Adult Fly

37. GCE BIOLOGY BY2 Reproductive Strategies Metamorphosis metamorphosis insect Choose an insect and drag it to the ‘insect’ box below. Decide what type of metamorphosis it has, then complete its life cycle by dragging the appropriate labels into the correct position on the diagram: complete metamorphosis incomplete metamorphosis egg larva nymph pupa chrysalis adult

38. GCE BIOLOGY BY2 Reproductive Strategies Parental Care Defending territory during embryo development(ex: male stickleback fish) Some fish fan eggs to give oxygen Provide shelter (nests, dens) Feeding young (birds, mammals) Protection from predators Training of offspring for survival Greater Parental Care = Greater Survival Rate

39. GCE BIOLOGY BY2 Reproductive Strategies BBC Nature videos otter cubs being moved frog maternal care Frogs hatch on the back Gharial hatching Slow loris Polar bear cubs Elephant gestation

40. GCE BIOLOGY BY2 Reproductive Strategies Unisexual and Hermaphrodites Unisexual = organisms that are either male or female (one sex) – Helps to increase variation in the offspring – Requires a partner Hermaphrodites = organisms that have both male and female sex organs – No need for a partner – Less variation in the offspring