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Plant Reproduction and Evolution Dynamics

Explore the process of plant reproduction from spores to seeds and learn about genetic diversity through meiosis. Dive into the evolution of plant species with natural selection theories and evidence of adaptation. Discover factors influencing population variation and contributing to the emergence of new plant species.

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Plant Reproduction and Evolution Dynamics

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  1. Sporophyte 2N, produces spores Non-vascular-to-vascular Spores-to-seeds Cones-to-flowers Motile-to-non-motile sperm Relative dominance in major plant lineages Gametophyte 1N, produces gametes

  2. Fig. 37.3

  3. Types of cell division • Mitosis: • growth, development & repair • Asexual reproduction (yields identical cells) • Occurs in somatic (body) cells • Meiosis • Sexual reproduction (yields different cells) • Occurs in specific reproductive cells

  4. A comparison of mitosis and meiosis (Part 1)

  5. Meiosis • Type of cell division that halves number of chromosomes • Process of 2 successive divisions • Chromosome number reduced in prophase I and anaphase I • Product is gamete, essential for sexual reproduction

  6. Meiosis occurs in gametophytes Male gametophyte • male = pollen grain • located within pollen sacs inside anther • female = embryo sac • ovules contained within ovary • embryo sac within ovule Female gametophyte

  7. Fig. 12.13a

  8. Overview of meiosis: how meiosis reduces chromosome number

  9. Results of alternative arrangements of two homologous chromosome pairs on the metaphase plate in meiosis I

  10. Crossing Over • exchange of genetic material between homologous portions of 2 non-sister chromatids (prophase I) • Increases genetic diversity Results of crossing over during meiosis

  11. Evolutionary advantage • asexual reproduction (mitosis) • easy, rapid, effective way to reproduce • useful in stable environment • lack of genetic diversity among offspring • sexual reproduction (meiosis) • promotes genetic variability • useful in dynamic environment

  12. Alternation of Generations

  13. Monecious or diecious Overview of angiosperm life cycle Polar nuclei  endosperm

  14. 1N, haploid No embryo No nutritive tissue 2N, diploid Embryo Nutritive tissue (endosperm, 3N) Spores vs. Seeds

  15. Plant Classification • Binomial nomenclature • (genus & species epithets) • Devised by Carolus Linnaeus in ca. 1750 • Species grouped by reproductive traits • More recently based on DNA sequences

  16. Plant Evolution How did we get so many species? Just what is a species?

  17. Fig. 1.5

  18. Fig. 1.1

  19. Fig. 1.6

  20. Fig. 15.4

  21. Fig. 15.3 Convergent evolution

  22. Theory of Natural Selection • Over-reproduction • Struggle for existence • Survival & reproduction of the fittest • Inheritance & accumulation of favorable traits

  23. Descent with modification

  24.  Remember: • - Natural selection occurs because of interactions between organisms and their environments. Because the environment varies in time & place, NS is situation dependent. • - Natural selection works to increase or decrease the occurrence of heritable traits. It “filters” existing variation, but does not generate variation. • Individuals are selected, but populations evolve. • - Populations are members of a species that interbreed. • - A population is the smallest unit that can evolve.

  25. Evolution of insecticide resistance in insect populations.

  26. Evolution of drug resistance in HIV

  27. Artificial selection: diverse vegetables derived from wild mustard

  28. 5.  Evidence of evolution Fossil record Convergent form & function Biogeography Homologous structures Embryological development Molecular (DNA) sequences

  29. Embryological evidence: all vertebrates have pharyngeal pouches – gills.

  30. Molecular evidence: e.g., DNA/RNA is universal for the genetic code. Other evidence: homologies basically follow the tree of life.  More closely related organisms have more homologous molecules.

  31. Evolution terms • Phenotype (expression of genes) vs. genotype (genetic make-up) • Micro (within a species) & macro (among species) changes • Evolution refers to changes in a population, not changes in an individual • Evolution (change) usually leads to adaptation of a species to environment (acclimation refers to changes in an individual)

  32. Sources of variation • Mutation in DNA sequences • Ca. 1 in 100,000 genes; most harmful • Most are harmful; some neutral or helpful • Migration • Genetic drift (in small populations) • Reproductive isolation • E.g., geographical, mechanical, temporal • Non-random mating (e.g., sexual selection) • Hybridization • Polyploidy

  33. Fig. 15.6 Geographic Isolation of Western & Eastern Redbud Species

  34. Fig. 15.7 Reproductive Isolation of Dutchmen’s Breeches and Squirrel Corn

  35. Fig. 15.8 Mechanical Isolation in Orchids

  36. Fig. 15.9

  37. Fig. 15.10 Hybridization & polyploidy is very common in plants

  38. Fig. 43.2

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