Plantae Flashcards
Characteristics of the Plant Kingdom
→ Eukaryotic → Multicellular → Autotrophic, they perform photosynthesis → Cell walls made of cellulose → Sessile
Alternations of Generations
→ Life cycle in plants
↪ A multicellular gametophyte ( Haploid n ) changes with a multicellular sporophyte ( Diploid 2n )
→ Depending on the plant, one stage is more dominant than the other
Animal vs Plant Life Cycles
→ Animals: Somatic cells (2n) undergo meiosis, producing gametes (n). During fertilization, two gametes fuse (n+n), producing a zygote (2n). The zygote matures into the adult animal via mitosis
→ Plants: A multicellular sporophyte (2n) divides by meiosis to produce haploid cells (n) (called spores in some plant groupings). The spores, via mitosis, develop into a multicellular gametophyte (n). The gametophyte matures and produces gametes (n). The gametes undergo fertilization forming a zygote. This zygote develops into the mature sporophyte.
Evolution of Plants
Evolved from green algae
Bryophytes
→ Common name Mosses and liverworts
→ A non vascular organism
→ Has a dominant generation of Gametophyte
→ Seedless, uses spores to reproduce
↪ Require water to move the spore to the female plant
→ They grow very low to the ground
Pteridophytes
→ Common Name is Ferns
→ Has a dominant Generation of sporophyte
→ Has a vascular system
→ Leaves are called Fronds
→ Seedless, reproduce via spores
↪ Spore cases called sori form on the underside of the fronds
↪ Sperm swim to egg through water droplets
Gymnosperms
→ Common Name is Conifers
→ The dominant generation is sporophytes
→ Reproduce using seeds
↪ Male cones are smaller and grow in clusters at the tips of branches
↪ Male cones produce pollen that is spread by wind to female cones that contain a sticky resin to trap the pollen
↪ Sperm + egg = seed (Diploid 2n)
↪ Seeds are ‘naked’ and develop on scales of female cones
Angiosperms
→ Basically any flowering plants (including plants that produce flowers when budding)
→ Has a dominant generation of Sporophyte
→ Pollen (male gamete) is spread by wind, animals, etc to egg to produce a seed ( Diploid 2n )
↪ Once seed is produced, a fruit is formed
↪ Fruit as a method of dispersing seeds (The fruits are adapted for dispersal, to be eaten, to get stuck in an animal’s fur or fly)
→ Only flower with fruit
→ The most common type of species
→ Classified into Monocots and Dicots
Monocots (Monocotyledons)
→ One cotyledon
↪ Endosperms remains as cotyledon expands
→ Veins run parallel in leaves
→ The stem contains random vascular bundles (collection of xylem and phloem tubes)
↪ Scattered in a complex pattern
→ Has petals in multiples of 3
→ Has a long fibrous root that branches out
Dicot (Dicotyledons)
→ Dicots have two cotyledons
↪ The endosperm withers as cotyledons expand
→ Dicot have netlike and branched veins
→ Vascular bundles in the stem are arranged in ring.
→ Has leaves in fours or fives or their multiples. These are called dicot petal
↪ Under each petal is a leaf like sepal
→ Has a long singular taproot that extends into the ground
Bryophyte Life Cycle
1) The gametophytes initiate the gametangia ( Reproductive Organs ) to produce the gametes [Haploid]
↪ The female gametangium is called the archegonium
↪ The male gametangium is called the antheridium
↪ These can be on different plants or the same plant
2) Sperm is released from the antheridium and take to an archegonium via water [Haploid]
3) The two gametes undergo fertilization and create a diploid zygote. This is the beginning of the sporophytic generation [Diploid]
↪ This reproduction is called oogamy - when a large non motile egg is fertilized by a motile sperm (remember that bryophytes have biflagellate sperm).
4) The egg divides via mitosis to form a diploid embryo [Diploid]
5) The material for the developing sporophyte is coming via placenta tissue [Diploid]
↪ Called matrotrophy as the material is moving via the cell wall
6) The mature Bryophyte has a top part that is a sporophyte ( blub called capsule and stem called seta ) while the bottom is a gametophyte. [Gametophyte is haploid while the sporophyte is diploid]
7) The capsule stores all the sperm that is produced via meiosis and the cycle repeats. [When haploid spore are released it is haploid]
Pteridophytes Life Cycle
1) Fern spores germinates into a heart-shaped haploid gametophyte that contains both male and female gonads. [Haploid]
2) As the young gametophyte matures, the sex organs become active. For male it is the antheridium and for the female it is the archegonium. [Haploid cells start to form]
3) Using water the sperm swim or get carried to the archegonium and fertilize the egg. [Diploid]
↪ Sperm is released in large numbers from many gametophytes that are in the same water as the sperm, so the sperm doesn’t have to be from the same gametophyte.
↪ There are spore cases under the fronds ( fern leaves ) called sori.
4) A diploid egg undergoes mitosis to form a embryonic sperm with tightly curled structures called fiddleheads that unfold as they grow into fronds [Diploid]
5) The mature frond has sori which are spore casings that hold spore and are on the fronds. [Spores are Haploid]
6) Spores formed via meiosis and released back into the air [Haploid]
Gymnosperms Life Cycle
The life cycles of these plants are long processes, some take 1000s of years.
→ They are generally heterosporous, producing strobili ( Pine cone or a structure with overlapping scales ) for male and female
1) The male and female cones produce microspores, which are stored in specially formed leaves called scales. [Microspores are Haploid]
↪ Each female cone carriers one bare, exposed ovule (a structure that contains the female gametophyte that gets fertilized by the sperm). These cones are sticky to catch flying sperm from the wind
2) Within the ovules, the cells undergo meiosis, producing 4 haploid cells. One cell survives as the megaspore and then divide via mitosis. The result is a female gametophyte that has 2 or 3 archegonia. [The gametes are Haploid]
3) Several strobilae make up a male cone which also produce microspores that undergo mitosis and produce pollen grains (male sex cells) [Haploid]
4) Wind blows the male pollen from the male strobili to the female strobili and the pollen fertilizes the egg, creating a diploid zygote. [Diploid]
5) Diploid Embryo via mitosis is created with gametophytic tissue that acts as a food reserve [Diploid]
6) Embryo matures into a young sporophyte [Diploid]
7) Then becomes a mature sporophyte [Diploid]
Angiosperms Life Cycle
Angiosperms undergo double pollination, which means two sperm cells are required to fertilize the egg.
1) A flower contains the male anther and the female ovary. Both of these undergoes meiosis resulting in microspores that are haploid in males and megaspores that are haploid in females. [Haploid]
2) Microspores from the male develop into pollen while the megaspores from females develop into eggs [Haploid]
3) When pollen contacts the egg, fertilization occurs forming a diploid zygote. (This usually happens via pollinators or sometimes the wind) [Diploid]
↪ Plants can self pollinate or cross pollinate
4) In the egg there is a dikaryotic cell that still needs to be fertilized, so another sperm does that forming a triploid cell called the endosperm. The endosperm nourishes the developing embryo [Triploid cell and diploid zygote]
5) Egg develops into an embryo which develops into a seed with simple fruit casing around it. [Diploid]
6) The seed is then either carried by the wind, carried on animal fur, by water, by expulsion or eaten and pooped by the animal. [Diploid]
7) Seed lay dormant due to the presence of certain hormones. When gone the seed can start the germination process. [Diploid]
8) The germinating seed develops into a mature sporophyte [Diploid]
Parts of a Flower
→ Stamen: Pollen producing part of the flower ↪ Anther: Carry and produce the pollen ↪ Filament: Hold up anthers → Petal: Attract Pollinators → Sepal: Help protect the developing bud → Pistil ↪ Stigma: Traps and holds pollen ↪ Style: Tube-like that holds the structure up and delivers pollen to the ovary where the ovules are ↪ Ovary: Female reproductive organ
Flower can be have only male or only female or both.
