PLANTS EVERYTHING YOU NEVER WANTED TO KNOW BUT
PLANTS EVERYTHING YOU NEVER WANTED TO KNOW BUT NEEDED TO FOR THE AP EXAM
Domain Eukarya Kingdom: Plants Domain Bacteria Domain Archaea 2007 -2008 Common ancestor Domain Eukarya
• Land plants evolved from green algae • Researchers have identified green algae called charophyceans as the closest relatives of land plants
Genetic Evidence • Comparisons of both nuclear and chloroplast genes – Point to charophyceans as the closest living relatives of land plants (a) Chara, a pond organism 10 mm 40 µm Figure 29. 3 a, b (b) Coleochaete orbicularis, a diskshaped charophycean (LM)
Animal vs. Plant life cycle Animal Plant diploid multicellular individual 2 n mitosis diploid multicellular sporophyte mitosis 2 n meiosis zygote 2 n fertilization haploid unicellular gametes 1 n no multicellular haploid zygote 2 n fertilization meiosis gametes 1 n spores 1 n mitosis haploid multicellular gametophyte 1 n alternation of generations
Pollen • Pollen eliminated the requirement for water for fertilization – spread through wind & animal
Angiosperm: flowering plants
Flower • Modified shoot with 4 rings of modified leaves – sepals – petals – stamens Anther Stamen Stigma Style Ovary Carpel Filament • male – carpel • female sepals petals stamens Petal Ovule Sepal adaptations through mutations carpel
• The life cycle of an angiosperm Key Anthers contain microsporangia. Each microsporangium contains microsporocytes (microspore mother cells) that divide by meiosis, producing microspores. 1 Haploid (n) Diploid (2 n) Microsporangium Anther Microsporocytes (2 n) Mature flower on sporophyte plant (2 n) When a seed germinates, the embryo develops into a mature sporophyte. MEIOSIS Microspore (n) Ovule with megasporangium (2 n) Ovary Tube cell Pollen grains MEIOSIS Stigma 3 In the megasporangium of each ovule, the megasporocyte divides by meiosis and produces four megaspores. The surviving megaspore in each ovule forms a female gametophyte (embryo sac). Embryo (2 n) Endosperm (food Supply) (3 n) 6 Generative cell Male gametophyte (in pollen grain) 7 Germinating Seed The zygote develops into an embryo that is packaged along with food into a seed. (The fruit tissues surrounding the seed are not shown). Microspores form pollen grains (containing male gametophytes). The generative cell will divide 2 to form two sperm. The tube cell will produce the pollen tube. Seed Megasporangium (n) Surviving megaspore (n) Seed coat (2 n) Pollen tube Sperm Pollen tube Style Female gametophyte (embryo sac) Antipodal cells Polar nuclei Synergids Egg (n) Pollen tube Zygote (2 n) Nucleus of developing endosperm (3 n) Egg Nucleus (n) Sperm (n) 4 After pollination, eventually two sperm nuclei are discharged in each ovule. FERTILIZATION Figure 30. 10 5 Double fertilization occurs. One sperm fertilizes the egg, forming a zygote. The other sperm combines with the two polar nuclei to form the nucleus of the endosperm, which is triploid in this example. Discharged sperm nuclei (n)
From Ovary to Fruit • A fruit – Develops from the ovary – Protects the enclosed seeds – Aids in the dispersal of seeds by wind or animals
Co-evolution: flowers & pollinators
Plant Structure, Growth, and Development
• An example of signal transduction in plants 2 Transduction 1 Reception 3 Response CYTOPLASM c. GMP Plasma membrane Second messenger produced Phytochrome activated by light Cell wall 2 One pathway uses c. GMP as a second messenger that activates a specific protein kinase. The other pathway involves an increase in cytoplasmic Ca 2+ that activates another specific protein kinase. Specific protein kinase 1 activated Transcription factor 1 NUCLEUS P Transcription factor 2 P Specific protein kinase 2 activated Transcription Light Translation 1 The light signal is detected by the phytochrome receptor, which then activates at least two signal transduction pathways. Figure 39. 4 Ca 2+ channel opened Ca 2+ 3 Both pathways lead to expression of genes for proteins that function in the de-etiolation (greening) response. De-etiolation (greening) response proteins
• The bending of a grass seedling toward light – Begins with the plant sensing the direction, quantity, and color of the light Figure 39. 1
• Xylem – Conducts most of the water and minerals – Includes dead cells called tracheids • Phloem – Distributes sugars, amino acids, and other organic products – Consists of living cells
- Slides: 16