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:
Edward Jenner inferred that a person who once had small pox cannot have it once again. So something is there in these persons which grows after the initial infection which interferes with the secondary infection resisting it.
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Explanation:</u></h3>
Edward Jenner is called the Father of Vaccination. Jenner noticed that the milkmaids who deal with the cows all the time don't generally suffer from the cowpox or small pox. Then as an Experiment, he took some sample from the pustules of the cow having pox and then cleaned it and injected the sample into a healthy child. Then when everyone of the locality suffered from the same disease, that child remained healthy. So that lead to infer that there are something in the pustule which lead to resist the secondary infection of this disease. So this lead to the invention of vaccines.
The answer is d. A large asteroid or comet impacted the Eartg
Answer:
The correct match for the terms with their description is given below:
Explanation:
- Gene: f) A sequence of nucleotides in DNA that codes for a functional product such as a protein.
- Nucleotide: d) The building blocks of nucleic acids, includes a phosphate, sugar and organic base.
- Chromosome: e) The structure that carries the DNA sequences
- Frameshift mutation a) The loss or addition of a nucleotide pair in a DNA strand.
- Point mutation: c) The substitution of one nucleotide pair for another in DNA strand.
- Genotype: g) The entire genetic makeup of an organism
- Phenotype: b) The physical and biochemical expression of the genotype.
