Plant Diversity Flashcards
What are charophytes the closest relative of
land plant (embryophyte)
4 key traits of land plants that are absent in green algae charophytes
- alternation of generations (multicellular, dependent embryos) - life cycle of plants
- walled spores produced in sporangia
- multicellular gametangia
- apical meristems: growth region in plants found within root tips and tips of new shoots and leaves
Sporangia
organ where sporophyte produces spores
Sporocytes
- diploid cells
- undergo meiosis to generate haploid spores
Sporopollenin
- contained in spore walls
- protect against dessication making them resistant to harsh environments
Archegonia
- female gametangia
- produce eggs and are the site of fertilization
Antheridia
- male gametangia
- the site of sperm production and release
Life cycles of non-vascular plants
- spore germinates into a gametophyte
- mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium
- sperm swim through a film of water to reach and fertilize the egg
- diploid zygote develops within archegonium, becomes an embryo via mitosis
- embryo will give rise to the diploid sporophyte
- sporophyte will produce spores which will be contained within the sporangia
Life cycles of seedless vascular plants
- sporophyte generation is the dominant and photosynthetic part of the life cycle
-underneath the sporophylls of sporophyte there are sporangia present
-spores will develop into the haploid gametophyte - in ferns the gametophytes are hermaphroditic
- need water for flagellated sperm to swim from antheridia and into archegonia for purposes of fertilizing egg
- fertilized egg becomes diploid zygote, gives rise to the diploid sporophyte
Sporophyll
spore bearing leaves
- underneath them there are sporangia present
Sorus
group of sporangium
4 common characteristics to all seeded vascular plants
- reduced gametophytes
- heterospory
- ovules
- pollen
Reduced gametophytes
- mosses and other bryophytes have life cycles dominated by gametophytes
- ferns and other seedless vascular plants have sporophyte-dominated life cycles
- continued in the vascular plant lineage that led to seed plants
- miniaturization allowed for an important evolutionary innovation in seed vascular plants
- tiny gametophytes can develop from spores within the sporangia of the parental sporophyte
- protects gametophyte from environmental stress
Homosporous
- non-vascular and most seedless vascular plants
- produce one type of spore of the same size
Heterosporous
- seed vascular plants
- produce spores of 2 different sizes and sexes by the sporophytes
Ovule
immature seed
Seed
fertilized ovule
Megasporangium/nucellus (diploid)
- produce megaspores that give rise to female gametophytes
- inner cell mass of ovule, comprising of diploid sporophytic cells
Megasporocyte (diploid)
- diploid cell that undergoes meiosis to produce four haploid megaspores
- at least one of the spores develops into the haploid female gametophyte
Megaspore (haploid)
- develop into female gametophytes within the ovule, where fertilization takes place, leading to the formation of seeds
Integument
- layer of sporophyte tissue (diploid) that envelops and protects the megasporangium and the megaspore
- develop into the seed coat when the ovule matures after fertilization
angiosperms have 2 - covered by ovary wall
gymnosperms have 1- uncovered
3 components that a mature seed contains
- the diploid integument which develops into the seed coat
- the haploid female gametophyte (food supply)
- the diploid embryo (will germinate to become a new sporophyte)
Microsporangium (diploid)
-produce microspores that give rise to male gametophytes
- pollen sac that contain microsporocytes
Microsporocytes (diploid)
- a diploid cell that undergoes meiosis to produce 4 haploid microspores
- each microspore will ultimately form a haploid pollen grain (male gametophyte)
Microspores (haploid)
- each microspore will ultimately form a haploid pollen grain (male gametophyte)
Life cycle of plants
-multicellular gametophyte (haploid) produces haploid gametes by mitosis
-fusion of gametes results in fertilization, rise to the diploid zygote
- zygote divides by mitosis, develops into a multicellular diploid sporophyte
- sporophyte produces haploid spores by meiosis
- spores divide by mitosis and develop into the gametophyte
Similarities and differences between zygotes and spores
similarities - both single cells that divide by mitosis to form a multicellular individual
difference - zygotes result from the fusion of two cells such as sperm and an egg (diploid)
- spores are not formed by fusion of 2 cells (haploid)
- zygotes produces sporophytes
- spores produce gametophytes
Apical Meristems
- comprise of embryonic cells and are the growth regions at plant tips (root tips and shoot tips) allowing plants to sustain continual growth in their length
Bryophytes
- non-vascular
ex. liverworts, hornworts, mosses - gametophytes are dominant part of the life cycle
Vascular tissue
- xylem and phloem
- allows vascular plants to grow tall compared to the non-vascular plants
