Angiosperms are plants that reproduce by means of flowers. Flowers are showy, colorful structures made of modified leaves. A flower usually contains both male and female reproductive structures. A flower can have up to four types of modified leaves: petals, sepals, carpels (which consist of a stigma, style, and ovary), and stamens (which consist of an anther and filament). Ovules and megasporocytes are present inside the ovary. Let's review the sequential stages of the angiosperm life cycle. The process that occurs in the ovary which initiates the development of female gametophytes is the division of a megasporocyte by meiosis. Inside an ovule, the megasporocyte (2n) undergoes meiosis to form four cells, but only one of these cells survives as the megaspore (n). The nucleus of the megaspore divides by mitosis three times, resulting in one large cell with eight haploid nuclei. Membranes then grow between these nuclei to form a multicellular structure called the embryo sac, which is the female gametophyte. The large egg cell is located at one end of the embryo sac. A diploid cell within the anther divides by meiosis to form four microspores (n). Each microspore (n) divides once by mitosis to form two cells. A tough wall is formed around the outside, creating a pollen grain, which contains a male gametophyte. Pollen grains are transferred by wind, water, or an animal to a sticky stigma in a flower of the same plant or another individual of the same species. After a pollen grain lands on the stigma, it forms a pollen tube that elongates downward through the style into the ovary. Two sperm nuclei (n) form inside the pollen tube. The pollen tube enters the ovary and releases the two sperm nuclei into the embryo sac. One sperm nucleus fertilizes the egg, forming a diploid zygote. The other sperm nucleus fuses with two nuclei in the center of the ovule to form a triploid (3n) cell that will develop into a nutritive tissue called endosperm. This process is called double fertilization. The triploid cell divides rapidly by mitosis to form endosperm, a tissue rich in starch, lipids, and proteins. The zygote divides by mitosis to form a sporophyte embryo with a rudimentary root and one or two cotyledons (seed leaves). The integuments of the ovule become a tough seed coat, with the embryo and endosperm inside. As the ovules develop into seeds, the ovary surrounding the ovules develops into the fruit, which will protect and help disperse the seeds. The fruit falls to the ground and seeds germinate. A seedling uses the food stored in the endosperm and cotyledons to grow until it can begin photosynthesis. The young plant grows into a mature sporophyte that produces flowers, and the cycle continues.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
27. Protists
Protist Life Cycles
Video duration:
3mPlay a video:
Related Videos
Related Practice