alternation of generations Life cycle
The plant life cycle consists of two alternating phases within the alternation of generations, the first phase that we discussed in class was the diploid phase also known as 2n. The diploid phase has DNA from both the female and male reproductive organs or also known as the sporophyte. The second phase is the haploid phase also known as n. This phase is demonstrated as having only one reproductive organ system; this also means that it can either have an archegonium (eggs) or antheridium (sperm). There are two processes that produce the two types of reproductive cells. There is mitosis and meiosis they produce either gametes or spores. The haploid stage is called the gametophyte(n) these are classified as reproductive cells that generate a sporophyte(2n) by the process of meiosis. The gametophyte is either antheridium which is male or archegonium which is female. Now these sporophytes become independent and form gametophytes. The gamete is produced by mitosis creates a new sporophyte in the diploid stage. The archegonium which is female shoot contains the archegonium which is on the top is a haploid(n0 that produces eggs. However, the antheridium which the male produces motile sperm that when enough water is produced can fertilize and swim to the egg. A zygote is produced from this process.
Characteristics of plants
Bryophytes classify as mosses, liverworts or hornworts.
· Contain non vascular tissue
· Dominant stage gametophyte
· First land plants
· Rely on water for reproduction
· Draw up water by osmosis
Mosses
· Most common
· Grow in areas with lots of water such as swamps, bogs, around streams or rainforest
· Adapt to wet habitats or nutrient poor soils
· Live in low temperatures
· Have rhizoids which are long thin cells that keep them in the ground and absorbs water and nutrients
Liverworts
· Have thin broad structures that draw up moisture form the surface of the ground
· Gametophyte produces structure that look green umbrellas – carry sperm and eggs
Hornworts
· Lives only in soil that is damp all year round
· Sporophyte looks like a green horn
Pteridophyta
· Climate became dry –adaptation resulted in the evolution of vascular plants
· Vascular plants – transport tubes that contain a xylem which brings water into plant through the roots and phloem which is a product of photosynthesis
· Results in larger plants and movement of nutrients
· Swimming sperm (flagellated) – swim from antheridium to archegonium
· Life cycle dominated by the saprophyte stage
· Don’t produce seeds
Clubmosses
· Small plant
· Lives in moist wetlands
· Looks like a small pine tree
Horsetails
· Grows a meter tall
· Nonphotosynthetic
· Leaves looking like scales are arranged in distinctive whorls and jointed together along their stems
Ferns
· True vascular tissue
· Strong roots
· Underground stems called rhizoids
· Large leaves called fronds
· Live in wet areas
Gymnosperm
· Seeded- naked
· Climate change of cooler and dryer conditions – dependent on non-seeded plants
· Gametophyte becomes smaller and more protected
· Asexual pores for sexual pollen for air distribution of gamete
· Development of embryo protection (seeds)
· Heterospory – male and female gametophyte
· Pollen containing male gametophyte
· True roots
· No longer requiring water for reproduction
Gnetophytes
· Reproductive scales are clustered into cones
Cycads
· Palm like plants
· Reproduce with large cones
Ginkgoes
· Alive when dinosaurs roamed the globe
· Only one type of species – Ginkg Biloba
Conifers
· 500+ species
· Pines, spruces, firs, cedars, redwood ext.
Angiosperm·
Flowering plants – covered seeds
· Evolution of specialized reproductive structures (flowers)
· Vascular tissue
· Fruit used to spread the angiosperm to new areas
Life cycle of plants
Every plant life cycle undergoes the alternation of generations. However, only in Bryophyta is the cycle gametophyte dominant. In Pteridophyta, Gymnospermae and Angiospermae, every cylce is sporophyte dominant. Every plant type has the qualities of the female archegonium, male antheridium, spores, and other characteristics. Bryophytes are non-vascular land plants, while the other three are vascular, and have xylem and phloem. Pteridophytes have sori (containing spores performing meiosis) underneath the fronds, while angiosperms have covered, protected seeds, and gymnosperms have "naked" seeds. In addition, bryophytes are the only of the four which is dioecious; the male and female gametes are found on seperate plants. The other three plant types are monoecious, with the female and male gametes both found on the same plant.
life cycle of bryophyta
life cycle of pteridophyta
life cycle of gymnosperm
life cycle of angiosperm
ORGANIZATION of angiosperm
Angiosperm
· Flowering plants – covered seeds
· Evolution of specialized reproductive structures (flowers)
· Vascular tissue
· Fruit used to spread the angiosperm to new areas
Leaves
· Stomata Functioning
· Stomata opening- absorb water and become bean shaped – causing the stomata to become bigger
· Stomata closing- lose water become flaccid and becomes bean shaped – causing stomata to close
Stems
· Moving minerals up and down plant
· Provide structural support for plant
· Growth for plant (height/width)
Roots
· Absorb water and minerals from the soil
· Anchor the plant into ground
Flower
· Attract pollinator
· Has for rings – sepals, pedals, stamen (m), carpel (f)
· Flowering plants – covered seeds
· Evolution of specialized reproductive structures (flowers)
· Vascular tissue
· Fruit used to spread the angiosperm to new areas
Leaves
· Stomata Functioning
· Stomata opening- absorb water and become bean shaped – causing the stomata to become bigger
· Stomata closing- lose water become flaccid and becomes bean shaped – causing stomata to close
Stems
· Moving minerals up and down plant
· Provide structural support for plant
· Growth for plant (height/width)
Roots
· Absorb water and minerals from the soil
· Anchor the plant into ground
Flower
· Attract pollinator
· Has for rings – sepals, pedals, stamen (m), carpel (f)