Answer:
In bryophytes, the sporophyte is minute and dependent on the relatively prominent and nutritionally independent gametophyte for resources. The moss gametophyte looks like a miniature herb, with tiny leaf-like photosynthetic organs. The gametophyte generation begins as a dormant spore, which germinates under appropriate conditions to produce filamentous and branching protonemal tissues. These form multicellular bud-like structures, each of which develops into a leafy shoot. The mature gametophytes produce male and female sexual organs, the antheridia and archegonia, respectively. The gametophyte is often sexually distinct, and plants are either male or female.
Each antheridium has an outer layer that encloses and protects thousands of motile sperm, which swim through available external water layer to the egg. Fertilization at the base of the cylindrical archegonium produces a diploid zygote which develops into an unbranched sporophyte. The sporophyte consists of a thin stalk attached to the gametophyte, and a capsule that encloses the sporophytic meiotic cells.
In recent years, the mosses Physcomitrella patens and Funaria hygrometrica have emerged as attractive model systems for studying gene function in non-vascular plants because of the relative ease of molecular manipulation by homologous recombination. Mutants affecting gametophyte development have been isolated and their analysis should provide insights into the molecular basis of gametophyte development in mosses.
Explanation:
Answer:
d. Epithelial tissues are nourished by blood vessels in adjacent tissues, thus diffusion is limited to thin tissues.
Explanation:
Epithelial tissues have tightly packed cells and have no space for blood vessels to be present between adjacent epithelial cells. The cells of the epithelial tissues get nutrients from the blood vessels of neighboring connective tissues.
Since the exchange of nutrients between the cells of the epithelial and connective tissues occurs through diffusion, epithelial tissues are only one to few cells layers thick to allow nutrient supply to all of its cells.
Answer:
The sun is nearly above you in the mornings, which makes your shadow short. In the evenings, the sun is nearly beside, infront or behind you, do you shadow is a lot longer.
Explanation:
Answer:
D. Chemoautotrophs
Explanation:
Autotrophs in plain are organisms that synthesize their own food while hetrotrophs are organisms that do not synthesize their own food.
Chemotrophs (Chemoautotrophs and Chemohetrotrophs) are a group of organisms that obtain their energy through the oxidation of inorganic molecules, These organisms require carbon to survive and reproduce.
Chemoautotrophs are able to produce inorganic molecules by the fixation of CO2 from their immediate environment. The energy required for this process is got from Nitrogen, Magnesium, Sulphur etc.
Chemohetrotrophs are a class of chemotrophs that are unable to synthesize their own food but rather ingest complex molecules like carbohydrates from the environment.
Phototrophs are a group of organisms unlike chemotrophs that depend on the source of light or sunlight for synthesizing its food or organic molecules.
Photoautotrophs are basically photosynthetic plants which are able to carry out photosynthesis ie the conversion of CO2 and H2O to give Glucose and Oxygen in the presence of sunlight.
Photohetrotrophs are a class of organisms that do not synthesize their own food but rely on other organisms or already made organic molecules.
