Transcript Slide 1
Lab • Pine Lifecycle • Lilly Lifecycle Dates for plant group origins: • • • • Mosses 475 Ferns 420 Gymnosperms 360 Angiosperms 160 The Pine Life cycle Fig. 30.9 PHYLUM CYCADOPHYTA PHYLUM GINKGOPHYTA Cycas revoluta PHYLUM GNETOPHYTA Gnetum Welwitschia Ovulate cones Ephedra PHYLUM CONIFEROPHYTA Douglas fir Common juniper Wollemia pine Pacific yew Bristlecone pine Sequoia Gnetophytes • 3 genera: Welwitschia, Ephedra, Gnetum • Mostly dioecious • Have more Similarities to angiosperms: – Have vessel elements, – Lack archegonia (except Ephedra) – Two sperm nuclei in pollen. Fertilizes two eggs in some groups. Analogous to double fertilization n angiosperms • Morphologically diverse group, grouped by genetic comparisons • Common ancestral pool long gone, a few remote descendents remaining. Gingko biloba • Dioecious, heterosporous • Dichotomous venation • Deciduous Cycads • • • • Leaves look like palms, ferns Makes cones Dioecious, herterosporous Pollen tube produces sperm inside !! Pollen (Staminate) Cone: • Produced yearly • Short lived- die after releasing pollen • Different species release pollen at different times to avoid hybridization • The male cone has the microsporangia on scale-like sporophylls . – (n) microspores from by meiosis – They develop into pollen grains – Produces millions of pollen grains per branch • Carried by wind- random mating Pollen • are the male gametophytes – just 4 cells ! – generative cell forms the pollen tube – Pine pollen have wing cells to keep them afloat in air • are covered with a tough sporopollenin. • are carried away by wind or animals until pollination occurs. • pollen grain will elongate a tube into the ovule and deliver sperm (nuclei) into the female gametophyte via pollen tube • No longer need film of water to fertilize Ovulate cone • very small and fleshy when young • Forms the “Pine Cone” with seeds – often matures over 2-3 years • form on branch tips to catch pollen • 2 megasporangia form on each scale or sporophyll – Megasporangia form 2 ovules – They become the 2 mature seeds per scale in the pine cone Ovule • Forms inside female (ovulate) cone • Megasporangia on sporophylls under go meiosis – one surviving (n) megaspore. • Megaspore grows inside by mitosis integuments (2n) to become female gametophyte – With 3 archegonia and eggs (pine). • Zygote develops into embryo, inside nutritive female gametophyte tissue. • Embryo goes dormant, integuments harden and ovule now becomes a seed Pine ovule Pine Megasporangia : ovulate cone Pine Ovule; female gametophyte & Archegonia Pine Microsporangia & pollen Staminate Ovulate Pine pollen & pollen tube Angiosperms • Flowers – attract pollinators • Ovary = Fruit • Ovules ( inside)=seeds The flower • Sepals • Petals • Stamens (male) – Anther - pollen – Filament • Carpel (female) – – – – Stigma Style Ovary Ovule-eggs Figure 30.13 Flower-pollinator relationships (a) A flower pollinated by honeybees. (b) A flower pollinated by hummingbirds. This honeybee is harvesting pollen The long, thin beak and tongue of this and Nectar (a sugary solution secreted rufous hummingbird enable the animal by flower glands) from a Scottish to probe flowers that secrete nectar broom flower. The flower has a tripping deep within floral tubes. Before the Mechanism that arches the stamens hummer leaves, anthers will dust its over the bee and dusts it with pollen, beak and head feathers with pollen. some of which will rub off onto the Many flowers that are pollinated by stigma of the next flower the bee visits. birds are red or pink, colors to which bird eyes are especially sensitive. (c) A flower pollinated by nocturnal animals. Some angiosperms, such as this cactus, depend mainly on nocturnal pollinators, including bats. Common adaptations of such plants include large, light-colored, highly fragrant flowers that nighttime pollinators can locate. The life cycle of an angiosperm Key Haploid (n) Diploid (2n) Anther Microsporangium Microsporocytes (2n) Mature flower on sporophyte plant (2n) MEIOSIS Microspore (n) Ovule with megasporangium (2n) Generative cell Tube cell Male gametophyte (in pollen grain) Ovary Stigma Megasporangium (n) Embryo (2n) Endosperm (food supply) (3n) Pollen tube Sperm Surviving megaspore (n) Seed Seed coat (2n) Female gametophyte (embryo sac) Nucleus of developing endosperm (3n) Pollen grains MEIOSIS Germinating seed Antipodal cells Polar nuclei Synergids Egg (n) Zygote (2n) Egg nucleus (n) Pollen tube Sperm (n) FERTILIZATION Discharged sperm nuclei (n) Pollen tube Style Gametophyte growth Angiosperm seed formation Flower cross section # 52 • • • • • Ovules Pistil Anthers Petals Sepals • Germinating pollen Lilly Anther