Biology Test 345

Tight junctions form a barrier that prevents substances from leaking between cells, ensuring that materials must pass through the cells rather than between them. This is particularly important in the lining of the stomach and intestines, where it prevents the passage of harmful substances. An interesting fact is that tight junctions are dynamic and can be temporarily broken and reformed, allowing for tissue growth and repair.

The primary function of nervous tissue is control and coordination of the body's functions. Neurons, the main cells of nervous tissue, transmit signals between different parts of the body. This allows for rapid communication and response to environmental changes. An interesting fact about neurons is that they are one of the longest living cells in the body and can't regenerate once damaged, highlighting the importance of protecting the nervous system.

Tourists visiting high altitude areas such as Rohtang Pass or Mansarovar, experience altitude sickness. Its symptoms include nausea, fatigue and heart palpitations. This is because in the low atmospheric pressure of high altitudes, the body does not get enough oxygen. But, gradually we get acclimatized and stop experiencing altitude sickness. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing breathing rate.

Hence, analogous structures are a result of convergent evolution %2D different structures evolving for the same function and hence having similarity.

(I) The afferent nerve fibres transmit impulses from tissues/organs to the CNS.

(II) The efferent fibres transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs.

Prokaryotic cells, such as bacteria, do not have a well-defined nucleus. Instead, their genetic material is located in a nucleoid region where DNA is not enclosed by a membrane. This is a key difference between prokaryotic and eukaryotic cells, the latter having a well-defined, membrane-bound nucleus.

Lysosomes are membrane-bound organelles containing hydrolytic enzymes that are responsible for digesting cellular waste, including damaged organelles, proteins, and other molecules. Due to their role in breaking down cellular debris, they are often referred to as the cell's "suicide bags."

Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. Through the process of cellular respiration, mitochondria break down glucose and oxygen to produce ATP, water, and carbon dioxide.

Radial symmetry is the arrangement of parts in an organ or organism such that cutting through the centre of the structure in any direction produces two halves that are mirror images of each other. All animals belonging to the cnidaria ( e.g., jellyfish) and echinodermata (e.g., starfish) are radially symmetrical.

The Golgi apparatus plays a crucial role in the packaging and modification of proteins. Proteins synthesized in the rough endoplasmic reticulum are transported to the Golgi apparatus, where they are modified, sorted, and packaged into vesicles for transport to their destination within or outside the cell.