Presentation on theme: "Plants A survey of Kingdom Plantae. Characteristics of Plants n All Plants are Producers - Photosynthetic n Plants are Multicellular n Plant cells have."— Presentation transcript:
Characteristics of Plants n All Plants are Producers - Photosynthetic n Plants are Multicellular n Plant cells have cell walls n Plants are Non Motile
Plant Evolution n Plants are thought to have evolved from Green Algae. n Modern Plants and Green Algae have the same type of chlorophyll, similar cell wall composition and both have starch as their food storing polysaccharide.
n Green Algae may be unicellular or multicellular and primarily live in aquatic environments n Modern Plants however are adapted to life on land
Advantages of Life in Aquatic Environment l Constant source of water - no risk of desiccation l Nutrients are readily available l Water provides support l Water is a medium for the transport of gametes l They have a moist surface for gas exchange
Life on Land n In order to survive on land plants must posses strategies or adaptations that compensate for the aforementioned advantages of life in water
Why are Bryophytes limited to Moist environments ¶ Sperm have to swim to egg · Only posses a thin cuticle so they are prone to desiccation.
Why Bryophytes are Limited in Size. ¶ With no vascular tissue there is no support for large sizes. · Also due to no vascular tissue materials are transported via diffusion…..this can only occur over a small area.
Reproduction In Bryophytes n Bryophytes undergo what is called an Alternation of Generations Ô An alternation between a haploid gametopyte generation and a diploid sporophyte generation.
Alternation of Generations in Bryophytes n See diagram on page 476
Tracheophytes n Tracheophytes are characterized by the presence of vascular tissue n Have “True” Roots Stems and leaves n There are two groups of tracheophytes:
What is Vascular Tissue? n Vascular tissue are parts of plants that are responsible for the transport of materials throughout the plant. n 2 types of Vascular Tissue ¶ Xylem - transports water and minerals · Phloem - transports “food”
Spore Producing Tracheophytes n An example of spore producing tracheophytes are Ferns
Gymnosperms and Angiosperms n These two groups of plants produce seeds. n Both have no need for water for reproduction and have true leaves, stems and roots. (needles are leaves). n In both the sporophyte is dominant (the plant is the sporophyte). The gametophytes are microscopic.
Gymnosperms n Conifers are gymnosperms. There seeds are in the female cones while pollen comes from the male cones. n They have advanced plant features (roots, leaves, stems) and usually restricted to harsh environments (cold). Why? n Thrive in cool climates, with poor soil, often found in moist seashore areas. n Some gymnosperms have leaves.
Life Cycle n They have a simple life cycle (page 479) and are often pollinated by wind. n Male gametophyte is the pollen grain n Female gametophyte is the Ovule n These gametophytes are contained within cones.
Life Cycle n Male cones release millions of pollen grains. n If a pollen grain lands on the ovule of a female cone a pollen tube will form n sperm will travel down the tube and fertilize the egg.
Life Cycle n A covering forms around the zygote and the food supply to form a seed. n When seed ripen the cones will open n seeds have papery wings and are dispersed by the wind.
Angiosperms n These are the most advanced plants and have adapted to a wide variety of habitats (everywhere you see flowers, you see angiosperms).
Angiosperms n These are the flowering plants: the reproductive structures of plants are located within the flower. n Male and female sex organs are in close proximity and are often placed to take advantage of wind or insects. n Pollen moves from one place to another to ensure fertilization of eggs. (see life cycle on page 480).
Types of Flowers Perfect Flowers n Flowers that have both male and female parts Imperfect Flowers n Flowers that have either male or female parts
Fertilization of a Flower n When a pollen grain lands on a stigma a pollen tube forms n The pollen tube grows down through the style n The tube nucleus directs the growth of the pollen tube n The sperm nuclei enter the ovule
Fertilization of a Flower n One sperm nucleus fuses with the egg to form a zygote n The other fuses with the two polar nuclei to form a cell that becomes the endosperm (Food Source) n This is know as double fertilization
Seed Structure After fertilization the ovule develops into a seed.
Fruit n After fertilization the ovary of the flower enlarges forming the fruit. The seed is contained in the fruit n As the fruit ripens the flower parts fall away.
Reasons for the success of Angiosperms n 1. Pollination is relatively easy (by wind, insects or self pollination) n 2. Flowers tend to attract insects (for pollen or nectar n 3. Seeds are protected by a seed coat (allowing seeds to pass undigested through most digestive tracts, then they grow in the free fertilizer)
Reasons for the success of Angiosperms n 4. Fruits are attractive to animals who in turn help disperse seeds (above). n 5. Seeds are able to suffer severe conditions such as fire, freezing, drought and then emerge when conditions are again suitable. n 6. Plants themselves have adapted to a wide variety of habitats.
Monocots vs Dicots n Vascular tissue n Parallel veins in leaves vs Netted Veins in leaves n Seeds n One Cotyledon vs Two Cotyledons n Flowers n petals in multiples of 3 vs petals in multiples of 4 or 5