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3 years ago

Crossing over happens in what stage of meiosis exactly?

2 answers:

5 0

There are several stages but the crossing over starts on the second stage. And the actual crossing sides happens on the following stage. Hope this helped :)

marshall27 [118]3 years ago

4 0

Answer:

In prophase stage, nearly to the metaphase.

Explanation:

Remember meiosis is the process in which the cell will divide and at the end will be 4 new cells with the half of genes each one. So at the begging of the process ( in the interphase) the cell will start to collect all the compounds, nutrients, etc. to duplicate its genetic information. The next stage ( the prophase), the cell will duplicate and recombine their genetic information ( that means cross over). In the next stage ( the metaphase), the four tetrads (the four similar genes that were duplicate), they start to align in the spindle fibers to start the first cell separation.

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Name two types of evidence used to support the theory of evolution. explain how scientist use each type of evidence to provide s

joja [24]

Answer:

There are many types of evidence which support the theory of evolution such as comparative anatomy, fossil records, phylogenetic relationship, embryology et cetera

Comparative anatomy includes homologous organs and analogous organs. They support divergent and convergent evolution respectively.

For example, the homologous structure of limb of humans, birds, bat, horse, whale et cetera show that they are made up of the same set of bones which are humerus, radius, ulna, carpals, metacarpals, and phalanges.

It shows divergent evolution and supports that these organisms have evolved from a common ancestor.

Embryological evidence: When early stages of embryological development of different organisms are compared, it is found that these stages are similar at different levels of development.

For example:

The appearance of pharyngeal-arch (gill-like structures) in vertebrates during embryo development.
Salamanders and terrestrial frogs pass through larval stages within an egg. They possess the features similar to aquatic larvae, however, when they hatched out the eggs being ready for life on land.

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3 years ago

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A. The African plate is breaking apart to form two separate plates.

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3 years ago

The ____________________ is the reproductive structure of gymnosperms.

Paha777 [63]

Answer:

seed cones and pollen cones

Explanation:

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The highlighted structure separates the oocyte from the externally located ________. zona pellucida primary follicle corona radi

Naya [18.7K]

Answer:

Granulosa cells

Explanation:

Foliculogenesis is a dynamic and complex process through which the follicle goes through many stages of development in a short period (approximately 60 days in humans and some chimpanzees).

The stages classification is based on morphological changes such as follicular size or diameter, the number of follicular cell layers, etcetera. These classifications might vary among authors but could be denominated as:

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De Graaf follicles (This is the one shown in the image)

Through each stage, there are certain modifications in the oocyte, follicular cells, and connective tissue. As the oocyte grows, the follicular cells might reach a size twice or three times bigger than the ones of the primordial follicles. Their shape also changes and they adopt an aspect of stratified epithelium. Their cytoplasm gets a granulous aspect, after what these cells receive the name of granulous cells. The De Graaf follicle characterizes for having a space named follicular antro that displaces the oocyte to one of the sides.

The oocyte at this point gets surrounded by zona pellucida and corona radiata .

The follicular antro (The highlighted structure) separates the oocyte from the externally located granulosa cells or follicular cells.

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