Key Biological and Geological Concepts Explained
Habitat
The place where an organism lives. It is normally characterized by physical features of the environment and dominant vegetation. A lake, a meadow, or a pond are examples of habitats.
Metamorphosis
A process of change from larva to adult that occurs in many invertebrates and amphibians.
Sporangia
The spore-producing organs of some plants and fungi.
Placenta
An organ made of maternal and fetal parts that allows the exchange of substances between the fetus and the mother during the embryonic development of mammals.
Vertebrates
Vertebrates possess an internal skeleton, or endoskeleton, in the spinal column. Their symmetric body can be divided into two parts, right and left, that are symmetrical. From the front to the back of their body, three parts are distinguished: the head, trunk, and tail. They generally have four limbs shaped like a paw, wing, or fin. The main element of the nervous system is in the front position. The brain is housed inside the skull, and the spinal cord is located within the backbone. Sense organs are located mainly in the head.
Invertebrate Classification
- Porifera: Very simple organization, body pierced by pores, aquatic, e.g., sponges.
- Cnidarians: Very simple organization, have a single hole surrounded by tentacles, aquatic, shaped like a polyp or jellyfish, e.g., jellyfish.
- Annelids: Soft body formed by similar rings, without a skeleton or shell, aquatic or live in humid places, e.g., earthworms.
- Mollusks: Soft, unsegmented body with a muscular foot, with a protective shell. The majority are aquatic, e.g., squid.
- Arthropods: With an articulated exoskeleton that allows movement, bilateral symmetry, live in all environments, e.g., grasshoppers.
- Echinoderms: Skeleton made of calcareous plates, radial symmetry, with ambulacral feet, aquatic, e.g., starfish.
Fungi
Fungi are living organisms fixed to the substrate and reproduce by spores but, unlike plants, they have heterotrophic nutrition.
- Decomposers: Those that live on the remains of other living beings, transforming them into inorganic matter useful for plants.
- Parasites: They live at the expense of a living animal or plant, causing disease.
- Symbiotic: They associate with other living things without hurting them.
Cellular Components
- Mitochondria: They are the power plants of the cell. Inside, energy is released, which is used to perform cellular functions and produce the cell’s own compounds.
- Membrane: A thin layer that surrounds the cell. It performs two main functions: it delimits the cell and separates it from the surrounding environment, and it regulates the entry and exit of substances.
- Wall: It is thick and rigid, situated outside the plasma membrane. It makes cells have a regular shape. The cell wall is made up of cellulose, a substance that is impermeable and resistant, and protects the cell. The plant cell wall has holes to allow the entry and exit of substances.
- Chloroplasts: Organelles containing a green pigment called chlorophyll. Photosynthesis takes place in them.
- Vacuoles: Membrane-bound cavities where substances are stored.
- Nucleus: The structure that contains a material, DNA, with the information to regulate the functions of the cell. Plant and animal cells have the nucleus separated from the cytoplasm by a membrane, which is why they are called eukaryotic cells. Bacterial cells lack a nuclear membrane and are thus called prokaryotic cells.
Primitive Atmosphere
The primitive atmosphere was very different in composition from the current one. The most abundant gases would be nitrogen and carbon dioxide, but there would be no oxygen.
Copernicus’ Statements
- The Sun is the center of the universe and motionless.
- The Earth is a planet.
- The Earth rotates on its axis and revolves around the Sun.
- The Moon orbits the Earth.
- The stars are fixed in a distant celestial field.
Copernicus was not wrong about anything.
Earth, Moon, and Sun
a) The Earth’s axis is tilted so that the equatorial plane is at an angle of 23 degrees with the plane of the Earth’s orbit. During some months, the Northern Hemisphere receives more hours of daylight, and the nights are shorter, while in other months, it is the Southern Hemisphere that receives more hours of light.
b) The point of Earth’s orbit furthest from the Sun is called aphelion; it is reached on July 4th. The point of Earth’s orbit nearest the Sun is called perihelion; it is reached on January 3rd.
c) The Moon has two movements: one around the Earth and another around its axis. As it takes the same time to complete the two movements, it always shows the same face.
d) An eclipse is the total or partial occultation of a star because another star gets in the way, preventing its vision. There are two types:
- Moon-Sun: Earth, Moon, Sun
- Sun-Moon: Sun, Moon, Earth
Sedimentary Rocks
When you look at some rocks, the grains are crystals if they are fragments of other rocks. Rocks of this type are called sedimentary. Depending on the size of the grains or fragments, they may be:
- Conglomerates: Over 2 mm.
- Sandstones: Less than 2 mm.
- Clays or Argillites: Such small fragments that a magnifying glass is needed to see them.