Death can be caused by breathing in lots of lead
Answer:
Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface. Permeable walls - allow gases to pass through. Extensive blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.
A locating overlapping sequences
Answer:
1. Chromatin condense into chromosomes.
4. Homologous chromosomes pair up (formation of tetrads).
5. Homologous chromosomes separate and move to poles.
2. Sister chromatids separate.
3. Chromosomes unravel in to chromatin.
Explanation:
This question portrays the process of meiosis in a cell. The ordered sequence of events in the options are:
1. Chromatin condense into chromosomes - This process occurs in the Prophase stage. Prior to the cell division, the nuclear material is found as Chromatin material. This Chromatin material then undergoes condensation to form visible chromosomes.
4. Homologous chromosomes pair up (formation of tetrads) - This process also occurs during the Prophase stage of meiosis I. In this stage, homologous chromosomes (similar but non-identical chromosomes received from each parent) are paired up side by side to form a structure known as TETRAD or BIVALENT.
5. Homologous chromosomes separate and move to poles - This process characterizes the Anaphase stage of meiosis I. Homologous chromosomes are pulled apart to opposite poles of the cell by spindle microtubules.
2. Sister chromatids separate - After meiosis I, meiosis II involving sister chromatids instead of homologous chromosomes follows. In the Anaphase stage of meiosis II specifically, sister chromatids are pulled apart towards opposite poles of the cell.
3. Chromosomes unravel in to chromatin - After the whole division process i.e. karyokinesis (division of the nuclear material), the chromosomes begin to unravel to form the CHROMATIN threads once again. This process occurs in the Telophase stage of meiosis.
Answer:
D. Molecules called pumps function to control active transport.
Explanation:
Active transport is one of the two types of transport (the other being passive transport). It is the type of transport in which substances move against their concentration gradient i.e. from a lower concentration to a higher concentration. Hence, due to this, energy input in form of ATP is required by the cell.
However, the process of active transport makes use of certain molecules called PUMPS to control it. The pumps moves ions/molecules against their concentration gradient. An example is the sodium-pottasium pump which moves sodium ions from a region of low conc. to a region of high conc.
