Answer:
Heart valves or the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole and the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
Explanation:
The heart tone “lub,” or S1, is caused by the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole.
The heart tone “dub,” or S2 ( a combination of A2 and P2), is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
Answer:
B
Explanation: I’m just using common sense. If part of the prairie grass is destroyed, that would mean less food for the bison. Which in turn would result in a decrease of Bison?
Prophase of mitosis do the chromosomes become distinctly visible in the microscope.
During metaphase, the nucleus dissolves and the cell's chromosomes condense and move together, aligning in the center of the dividing cell. At this stage, the chromosomes are distinguishable when viewed through a microscope. The first stage of mitosis and of meiosis I and II.
During prophase the chromosomes become visible as distinct structures, the nuclear envelope breaks down, and a spindle forms (Meiotic prophase I is more complex, and includes synapsis of homologous chromosomes and crossing over). During Prophase chromosomes become Clearly visible, nuclear envelope disappears, kinetochores and spindle fibers form.
To learn more about prophase , here
brainly.com/question/13883655
#SPJ4
Number 3 is correct
Concept; an abstract idea or general notion
Answer:
d. xylem and phloem
Explanation: plants possess vascular bundles.these are bundles which includes xylem and phloem tissues and transport useful substances to various plant cells.
New Xylem and phloem are formed from the vascular cambium which divides into new cells .
Xylem and phloem are thin and slender with pipe-like structure.
The xylem transports water and dissolved nutrients to the cells where they are needed.
The phloem transports the product of photosynthesis (sugar) to parts what they are used up or stored .
Xylem cells are dead and consists in vessels,trachieds and xylem parenchyma.
Phloem cells are dead and consists in sieves cell, companion cells, phloem parenchyma and phloem fibres.
