A condyloid joint (also called condylar, ellipsoidal, or bicondylar) is an ovoid articular surface, or condyle that is received into an elliptical cavity. This permits movement in two planes, allowing flexion, extension, adduction, abduction, and circumduction.

Oxygen is required by all living beings for respiration and for burning materials. This is balanced by green plants. Green plants take in carbon dioxide and release oxygen during the process of photosynthesis. Hence, the gases become balanced in the atmosphere.

Some characteristic features of Euglenoids are as follows.

• Euglenoids (such as Euglena) are unicellular protists commonly found in fresh water.

• Instead of cell wall, a protein-rich cell membrane known as pellicle is present.

• They bear two flagella on the anterior end of the body.

• A small light sensitive eye spot is present.

• They contain photosynthetic pigments such as chlorophyll and can thus prepare their own food. However, in absence of light, they behave similar to heterotrophs by capturing other small aquatic organisms.

• They have both plant and animal-like features, which makes them difficult to classify and hence they are called as connecting link between plants and animals.

The advantages of Asexual Reproduction are:

• It is a faster means of reproduction  
• Less energy required for reproduction
• Number of progeny produced is more

The disadvantage of Asexual Reproduction is:

• The daughter offspring look exactly and have the same genetic material as the parent
  lack of genetic variation. So as a result the population may go extinct with dramatic changes in environment.

The advantage of Sexual Reproduction is:

• It allows for genetic variation due to the involvement of two parents
   

The advantages of Sexual Reproduction are:

The Hayflick limit or Hayflick phenomenon is the number of times a normal human cell population will divide before cell division stops. 

Cell division is simpler in prokaryotes than eukaryotes because prokaryotic cells themselves are simpler. Prokaryotic cells have a single circular chromosome, no nucleus, and few other cell structures. Eukaryotic cells, in contrast, have multiple chromosomes contained within a nucleus, and many other organelles. All of these cell parts must be duplicated and then separated when the cell divides. A chromosome is a coiled structure made of DNA and protein, and will be the focus of a subsequent concept.

The condensed chromatin is folded and tightly coiled, like a coiled telephone cord, allowing the cell’s DNA to be packed into the nucleus.

Before a cell can divide, it must first replicate its DNA so that each of the two daughter cells will receive a complete copy of the DNA. The two identical chromosomes that result from DNA replication are referred to as sister chromatids. Sister chromatids are held together by proteins at a region of the chromosome called the centromere.

Step 1

Acetyl Co-A combines with a four-carbon compound, oxaloacetate, and releases the CoA group resulting in a six-carbon molecule called citrate.

Step 2

In the second step, citrate gets converted to isocitrate, an isomer of citrate. This is a two-step process. Citrate first loses a water molecule and then gains one to form isocitrate.

Step 3

The third step involves oxidation of isocitrate. A molecule of carbon dioxide is released leaving behind a five-carbon molecule, ɑ-ketoglutarate. NAD⁺ gets reduced to NADH. The entire process is catalyzed by the enzyme isocitrate dehydrogenase.

Step 4

Here, ɑ-ketoglutarate is oxidized reducing NAD⁺ to NADH and releasing a molecule of carbon dioxide.

CoA is picked up by the remaining four-carbon molecules forming an unstable compound succinyl CoA. ɑ-ketoglutarate dehydrogenase catalyzes the entire process.

Step 5

CoA from succinyl CoA is replaced with a phosphate group. It is then transferred to ADP to make ATP. Succinate, a four-carbon molecule is produced in this step.

Step 6

Succinate is oxidized to fumarate. Two hydrogen atoms are transferred to FAD to produce FADH₂. FADH₂ transfers its electrons directly to the electron transport chain since the enzyme carrying out the reaction is embedded in the inner membrane of mitochondria.

Step 7

A water molecule is added to fumarate which is then converted to malate.

Step 8

The oxidation of malate regenerates oxaloacetate, a four-carbon compound, and another molecule of NAD⁺ is reduced to NADH in this step.

• Kranz anatomy is the special arrangement of the cells found in the C4 plants
• The bundle sheath cells form several layers around the vascular bundles.
• The chloroplasts of bundle sheath cells are large and more in number, they have thick walls and no intercellular spaces.
• Mesophyll cells are undifferentiated and arranged in concentric layers around the vascular bundles.

The eight steps of the citric acid cycle are a series of redox, dehydration, hydration, and decarboxylation reactions. Each turn of the cycle forms one GTP or ATP as well as three NADH molecules and one FADH2 molecule, which will be used in further steps of cellular respiration to produce ATP for the cell. The citric acid cycle, also known as the Krebs cycle or the tricarboxylic acid cycle, is at the center of cellular metabolism, playing a starring role in both the process of energy production and biosynthesis. It finishes the sugar-breaking job started in glycolysis and fuels the production of ATP in the process. In eukaryotes, the citric acid cycle takes place in the matrix of the mitochondria, just like the conversion of pyruvate to acetyl CoAstart text, C, o, A, end text. In prokaryotes, these steps both take place in the cytoplasm.

The Krebs cycle (named after Hans Krebs) is a part of cellular respiration. Its other names are the citric acidity cycle, and the tricarboxylic acid cycle (TCA cycle). ... The Krebs cycle comes after the link reaction and provides the hydrogen and electrons needed for the electron transport chain. The main function of the Krebs cycle is to produce electron carriers that can be used in the last step of cellular respiration. The citric acid cycle, also known as the Krebs cycle or the tricarboxylic acid cycle, is at the center of cellular metabolism, playing a starring role in both the process of energy production and biosynthesis. It finishes the sugar-breaking job started in glycolysis and fuels the production of ATP in the process.

Photorespiration is the wasteful process because, it prevent plant from using their ATP and NADPH to synthesize carbohydrates.rubisco the enzymes which fixer CO₂ during for O₂ fixation during photorespiration.

The mucosa of stomach has gastric glands. Gastric glands have three major types of cells namely
(i) mucus neck cells which secrete mucus;
(ii) peptic or chief cells which secrete the proenzyme pepsinogen; and
(iii) parietal or oxyntic cells which secrete HC1 and intrinsic factor (factor essential for absorption of vitamin B12).

All surfaces of the leaf have some amount of stomata for regulating gas exchange for photosynthesis. However, the lower epidermis (the underside of the leaf) has more, because it is more often in the shade and so it is cooler, which means evaporation won't take place as much. Dicot leaves are also called as dorsiventral leaves because they possess distinct dorsal and ventral sides. Monocot leaves are called isobilateral leaves since both the sides of monocot leaves are more or less similar.