* 29 Flashcards
closest relatives of plants: characteristics
Charophytes (algae): share the following 4 characteristics
- Distinctive circular rings of proteins in the plasma membrane. These rings synthesize the cellulose microfibrils of the cell wall. In contrast, noncharophyte algae have linear sets of proteins that synthesize cellulose.
- Peroxisomes that contain enzymes that help minimize the loss of organic products resulting from photorespiration
- Similar structure of flagellated sperm
- Particular details of cell division occur only in land plants and certain charophytes. For example, a group of microtubules known as the PHRAGMOPLAST forms btwn the daughter nuclei of a dividing cell. A cell plate then develops in the middle of the phragmplast, across the midline of the dividing cell. The cell plate gives rise to a new cross wall that separates the daughter cells.
closest relatives of plants: genera
Chara and Coleochaete
sporopollenin
In charophytes, a layer of a durable polymer that prevents exposed zygotes from drying out. A similar chemical adaptation is found in the tough sporopollenin walls that encase the spores of plants; makes their walls tough and resistant to harsh environments –> enables spores to be dispersed thru dry air w/o harm.
embrophyte
Alternate name for land plants that refers to their shared derived trait of multicellular, dependent embryos. Another name for land plants.
- As part of a life cycle w/ alternation of generations, multicellular plant embryos develop from zygotes that are retained within the tissues of the female parent (a gametophyte).
- The parental tissues provide the developing embryo w/ nutrients, such as sugars and amino acids.
- The embryo has specialized PLACENTAL TRANSFER CELLS, sometimes present in the adjacent maternal tissue as well, which enhance the transfer of nutrients from parent to embryo thru elaborate ingrowths of the wall surface (plasma membrane and cell wall).
Derived traits of land plants:
- alternation of generations (w/ an associated trait of multicellular, dependent embryos)
- walled spores produced in sporangia
- multicellular gametangia
- apical meristems
alternation of generations
- The life cycles of all land plants alternate btwn 2 generations of multicellular organisms: gametophytes and sporophytes.
Steps:
1. The gametophyte produces haploid gametes by mitosis.
2. Two gametes unite and form a diploid zygote.
3. The zygote develops into a multicellular diploid sporophyte.
4. Specialized cells of the sporophyte will undergo meiosis and produce haploid spores.
5. The spores will then develop into the multicellular gametophytes. w/o fusing w/ another spore
spore
- Meiosis in a mature sporophyte produces haploid spores, reproductive cells that can develop into a new haploid organism w/o fusing w/ another cell.
- Mitotic division of the spore cell produces a new multicellular gametophyte, and the cycle begins again.
sporangia
The sporophyte has multicellular organs called sporangia that produce the spores. The outer tissues of the sporangium protect the developing spores until they are released into the air.
sporocytes
Within a sporangium, diploid cells called sporocytes, or spore mother cells, undergo meiosis and generate the haploid spores.
Charophytes vs land plants: spores
- Multicellular sporangia that produce spores w/ sporopollenin-enriched walls are key terrestrial adaptations of land plants.
- Charophytes also produce spores, but they lack multicellular sporangia, and their flagellated, water-dispersed spores lack sporopollenin.
gametangium
Multicellular plant structure in which gametes are formed.
archegonia
- Female gametangia.
- Each archegonium is a pear-shaped organ that produces a single nonmotile egg retained within the bulbous part of the organ.
- Each egg is fertilized within an archegonium.
antheridia
- Male gametangia.
- Produce sperm and release them into the environment. -
- In many groups of present-day plants, the sperm have flagella and swim to the eggs thru water droplets or a film of water.
apical meristems
- Localized regions of cell division at the tips of roots and shoots; enable the plant to grow in length.
- Cells produced by apical meristems differentiate into the outer epidermis, which protects the body, and various types of internal tissues.
- Shoot apical meristems generate leaves in most plants.
cuticle
- The epidermis in many plant species has a covering, the cuticle, which consists of wax and other polymers.
- Acts as waterproofing, helping prevent excessive water loss, while also providing some protection from microbial attack.
secondary compounds: description
- Many land plants produce molecules called secondary compounds, so named b/c they’re products of 2ndary metabolic pathways – side branches off the primary metabolic pathways that produce the lipids, carbs, amino acids, and other compounds common to all organisms.
- Another derived trait that relates to terrestrial life.
secondary compounds: examples
- so named because they are products of secondary
metabolic pathways—side branches off the primary metabolic
pathways that produce the lipids, carbohydrates, amino acids,
and other compounds common to all organisms. - Alkaloids, terpenes, tannins, flavonoids.
- The first three have a bitter taste, strong odor, or toxic effect that helps defend against herbivores and parasites.
- Flavonoids absorb UV radiation, and some related compounds deter attack by pathogens.
vascular tissue
Cells joined into tubes that transport water and nutrients throughout the plant body.
bryophyte
Commonly used informally to refer to nonvascular plants.
Vascular vs non-vascular plants
- Shared derived traits: multicellular embryos, apical meristems
- Non-vasculars lack roots and true leaves
- Vasculars comprise 93 percent of all extant plant species
- In nonvasculars, the haploid gametophytes are the dominant stage of the life cycle – larger and longer-living than sporophytes
grade
- A group of organisms that share the same level of organizational complexity or share a key adaptation.
- Don’t necessarily share the same ancestry.
seedless vascular plants
- Lycophytes and pterophytes, members of a grade
- Pterophytes share a more recent common ancestor w/ seed plants.
seed
- An embryo packaged w/ a supply of nutrients inside a protective coat.
- Two groups: gymnosperms and angiosperms.