Aligators and Crocodiles

Alligators and crocodiles are carnivorous reptiles with a tough, scaly hide. Crocodiles and alligators have not evolved much for around 55 million years. Surprisingly, their ancestors existed even during the era of dinosaurs. Both have dome pressure receptors on their skin. These receptors control water pressure and detect ripples in the water while swimming. Crocodiles live in salty seawater and have a long V-shaped head. Many crocodile teeth protrude outside along the jaw. Crocodile teeth are sharp and pointed because they’re made to tear. Crocodiles are more aggressive and are lighter in color in comparison to alligators. Alligators live in freshwater. The heads of alligators are broader and shorter, having an appearance of a “U” shape. Since the upper jaw of an alligator is wider than the lower one, its teeth are mostly hidden, except for some teeth on the top. The alligator jaw is designed for crushing rather than tearing the prey. This is why they have cone-shaped teeth instead of the pointed ones.  Crocodiles are three feet longer on average than alligators. Alligators are generally harmless to humans and prefer to flee when they see people. Crocodiles are aggressive and tend to attack anything close to them, including humans. The dome pressure receptors of alligators can be seen as tiny black spots near their jaw. Crocodiles have translucent dome pressure receptors dispersed throughout their bodies, which makes them good swimmers compared to alligators. Crocodiles have salt glands on their tongues, allowing them to osmoregulate in salty environments. Unlike crocodiles, alligators do not need salt glands being freshwater animals.


Positively charged particles located inside an atom are called protons, while the particles with a neutral charge are called neutrons. Both are located in the nucleus, or center, of the atom. The particles that have a negative charge are called electrons. In contrast to the neutrons and protons, electrons have a negative charge located outside the nucleus. The atomic number describes the number of protons present in the nucleus. Atomic mass, or mass number, is the sum of protons and neutrons present in an atom. Atoms of the same element having the same atomic number but different atomic masses are isotopes. In contrast to isotopes, isotones are atoms of different elements that have the same number of neutrons. Atoms that belong to different elements that have the same mass number are called isobars. 

Chemical bonding is an interaction of atoms or ions with each other. Electrons play a significant role in the formation of such bonds. An ionic bond is formed when an electron is transferred entirely from one atom to another. In some cases, electrons are shared by two or more atoms to form a covalent bond. When the bonds are formed, exothermic reactions release heat; when the bonds break, endothermic reactions absorb heat. 


Cells, which are structural and functional units of living organisms, are divided into two main types: prokaryotic and eukaryotic. Unlike prokaryotes, eukaryotes have a clearly defined and developed nucleus in their cells. Both plant cells and animal cells are eukaryotic. Plant and animal cells share some common features, including the presence of specific organelles, i.e., mitochondria, well-defined nucleus, and endoplasmic reticulum. Additionally, both have cell membranes for protection. In contrast to rectangular-shaped plant cells, animal cells have irregular, almost round shapes. The outer membrane in plants is the cell wall covering the cell membrane, while in animal cells the outer membrane is the cell membrane. 

Vacuoles are membrane-bounded organelles in the cells. Plant cells have a single large vacuole to keep the water balanced in cells. In contrast, animal cells have multiple small vacuoles to assist in sequestering waste material. Moreover, animal cells have centrioles, while plant cells do not. Chloroplasts, a type of plastids, are present only in plants. Chloroplasts are involved in photosynthesis and have green pigment. Chlorophyll is a green pigment present in chloroplasts that absorb blue and red light from the sun and convert it into chemical energy. The central part of the cell is the nucleus which contains all information to regulate the cell.

Mammals and Reptiles

Mammals and reptiles belong to the phylum Chordata of the kingdom Animalia. They have four limbs, a sophisticated nervous system, and a closed circulatory system with a heart. Mammals are warm-blooded animals, while reptiles are cold-blooded animals. Reptiles are a more diverse group as compared to mammals, with more than 8000 species. The main difference between mammals and reptiles is that mammals have mammary glands that produce milk for their babies, while reptiles don’t. The mammalian epidermis is covered in hair, whereas the reptile epidermis is covered in scales. In comparison to reptiles, mammals have a faster metabolism. Mammals are viviparous, which means that they give birth to their young. Reptiles are oviparous animals, i.e., they lay eggs.

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Matter is anything that has volume and mass, while the substance is matter with a particular composition and chemical properties. Elements or compounds are examples of a substance. Compounds are formed when two or more elements combine in a fixed ratio (by mass). An atom is the smallest particle of an element. Atom loses or gains electrons to become a cation, i.e., positive ion, or anion, i.e., negative ion. Oxidation is the process in which an atom loses an electron, while reduction is the process in which an atom gains an electron. Molecules are formed when two or more atoms combine. Molecules can be homoatomic, consisting of similar atoms, or heteroatomic, consisting of different atoms. Atomicity is the term attributed to molecules that tell about the number of atoms present in a molecule. For instance, the atomicity of a glucose molecule is 24 because six atoms of carbon and oxygen individually combine with 12 atoms of hydrogen to form a glucose molecule with 24 atoms in it. 


The heterosphere and the homosphere are the two primary layers of the atmosphere. They are different in their gas compositions and altitudes. The homosphere is the lower part of the atmosphere, which extends up to 60 miles from the earth, and the heterosphere is the upper part that extends above 60 miles from the earth. The homosphere is divided into three regions: mesosphere, stratosphere, and troposphere, whereas the heterosphere includes the thermosphere and exosphere. Each layer’s temperature gradient depends on several factors such as distance from the sea level, solar radiation, latitude, ocean currents, and layers classification. The temperature rises with altitude in some layers and falls in others. The troposphere is cloudy and relatively humid, and its temperature gradient declines with height. The stratosphere is cloudless and dry, and its temperature gradient increase with height. In the mesosphere, temperature fall with altitude. The heat source is primarily in the stratosphere because the mesosphere has few gas molecules to absorb the Sun’s radiation. The mesosphere is extremely cold, particularly at the top. Temperatures rise with altitude in the thermosphere due to the extremely low density of molecules found here. It is devoid of both clouds and water vapor.


Organisms in kingdom Animalia can be either invertebrates (animals without a backbone) or vertebrates (animals with a backbone). Mammals are warm-blooded vertebrates covered with fur. Warm-blooded animals can maintain a nearly constant body temperature regardless of the temperature of their surroundings. Cold-blooded animals, however, are unable to regulate their body temperature in response to the temperature of their surroundings.

Mammals are classified into three major groups, i.e., monotremes, marsupial, and placental mammals, which are based on how they reproduce their offspring. Monotremes, which lay eggs, are an ancient type of mammal. Marsupial Mammals give birth to immature offspring, which grow in a pouch on the mother’s belly. In contrast to the other two, Placental mammals give birth to fully developed offspring. The umbilical cord from the mother feeds the baby inside the placenta. There are several animal coats, including blubber, fur, spines, and scales. Blubber is a thick layer of fat beneath the skin of all marine mammals. Fur is also present in some mammals containing two layers outer fur and inner underfur. The outer fur vent away moisture, keeping the underfur dry.


A microscope is an optical device used to let us observe objects invisible to the naked eye. A compound microscope uses a beam of light to illuminate an object, while an electron microscope uses a beam of electrons to illuminate an object. Compound microscopes employ three lenses, i.e., eyepiece lens, condenser lens, and objective lens. The condenser lens focuses the light source onto the specimen. At magnifications of 400x and higher, these lenses are extremely useful. If a light source isn’t focused, the specimen becomes fuzzy. Different condenser lenses are available based on the diverse range of adjustable aperture that helps control the light beam diameter. An aplanatic condenser lens, for instance, corrects spherical aberrations caused by light ray refraction, thus sharpening the view; and the achromatic condenser does color correcting in high magnification devices. The eyepiece lens is used to view the specimen on the slide. However, the objective lens is in the closest proximity to the specimen. A typical microscope might include several of these lenses to increase magnification. These lenses are usually built to standard specifications and may include interchangeable components that allow them to be used with different microscopes.


Proteins are complex structures made up of amino acids that fold. Four different protein structures include primary, secondary, tertiary, and quaternary proteins. Primary proteins are linear sequences of amino acids, while the secondary structure is folded. Secondary structures arise within a polypeptide chain due to the bonding between backbone atoms. The two most prevalent secondary structures in a polypeptide chain are alpha helixes and beta-pleated sheets. These two structural elements are the first major steps in folding a polypeptide chain. The primary distinction between the alpha helix and beta pleated sheet is their structure; they have two distinct shapes, and each performs a specific function. Dihedral angles of peptide bonds determine the secondary structure. However, as the level of protein structure gets higher from secondary, hydrogen bonding begins to play a significant role. Folding in space by polypeptide chains sometimes involves disulfide bonds which determine the tertiary structure. Multiple polypeptides combine to form subunits. The formation of a quaternary structure occurs when folded polypeptide subunits bind to complex functional proteins.

Electrochemical Cell

A simple electrochemical cell comprises two rods called electrodes, immersed in an electrolyte and connected by an electrical conductor, i.e., a wire. Two electrodes are essentially made up of different metals. The electrolyte can be an acid solution, an alkaline solution, a salt solution, or even a lemon or orange extract. An electrolyte is a medium containing ions that conducts electricity through ionic movement but not by electrons. The negative or reducing electrode of an electrochemical cell that loses electrons to the external circuit and oxidizes during an electrochemical reaction is known as the anode.

In contrast, the cathode is the positive or oxidizing electrode that receives electrons from the external circuit and reduces them during the electrochemical reaction. These electrochemical cells can either be rechargeable( secondary cells) or non-rechargeable (primary cells). A Voltaic or Galvanic cell is the one in which the chemical energy is transformed into electrical energy with spontaneous redox reactions. The anode used in these voltaic cells is negative, while the cathode is positive. However, the electrical energy in electrolytic cells is transformed into chemical energy with non-spontaneous redox reactions. These cells feature a positively charged anode and a negatively charged cathode.

Poikilothermic and Homeothermic Animals

Poikilothermic animals, or cold-blooded animals, cannot regulate their body temperature in response to the temperature of their surroundings. Cold-blooded don’t have a constant body temperature since their bodies adjust to the temperature of their surroundings. They cannot survive under harsh temperatures conditions. Further, excessively stored fat promotes overheating in cold-blooded animals’ bodies, which might lead to death. On the other hand, warm-blooded or homeothermic animals can maintain a fairly constant body temperature regardless of the environmental temperature. Body temperatures of warm-blooded are usually consistent, ranging from 35 to 40 degrees Celsius. Homeothermic animals’ proteins are not temperature-specific, but cold-blooded animals’ proteins are. Cold-blooded animals’ metabolic rates depend on the environment’s temperature, in contrast to warm-blooded animals. Cold-blooded animals are resistant to microbes; when infected, they lower their body temperature to protect themselves. Warm-blooded animals have a considerably stronger immune system than cold-blooded species. Warm-blooded animals adjust to extreme changes in temperature and environmental conditions efficiently. Warm-blooded animals need fat to keep their bodies warm, vital for whales and seals who dwell in cold climates.

Renewable and Non-renewable Energy

There are two types of natural resources: renewable and non-renewable. Sunlight, wind, and tidal energy are examples of renewable resources; another example is uranium, which is more uncommon and controversial because many people consider it non-renewable. Renewable natural resources can not be depleted. Non-renewable resources, on the other hand, cannot be immediately replaced once they run out. Fossil fuels such as coal, petroleum, and natural gas, as well as rare minerals found in meteorites, are examples of non-renewable resources. Countries must have a cost-effective and accessible infrastructure to have non-renewable energy sources. Compared to non-renewable energy, most renewable resources emit less carbon and have a smaller carbon footprint. Renewable energy has a higher upfront cost and requires a larger land or offshore area, especially for solar farms and wind farms, compared to non-renewable energy.