Cell Cycle, DNA Replication, and Mitosis Explained
The Cell Cycle
The cell cycle involves:
- Doubling of hereditary material, which is then equally divided between daughter cells.
- Division of the cytoplasm into two.
The cell cycle is a series of changes a cell undergoes from one division to the next, ultimately resulting in two daughter cells.
Cell Cycle Control
Cell cycle control occurs at the molecular level, regulated by cytoplasmic proteins, including cyclins and kinases. Checkpoints determine if the cell receives a signal to divide; if not, it enters
Read MoreEvolutionary Evidence and Human Origins
Evidence for Evolution
Testing Status
Evolutionary evidence is based on observations of intermediate species. For example, the platypus exhibits characteristics of both mammals and reptiles.
Biological Tests
Species differ across geographical areas, with greater differences observed in more isolated regions. An example is the 13 species of finches found in the Galapagos Islands.
Paleontological Testing
Comparing fossils with present-day animals reveals differences and similarities between past and current
Read MoreSensory Receptors and the Human Body Systems
Sensory Receptors
Structures formed by specialized nerve cells to capture and transform stimuli into nerve impulses.
According to Stimuli Captured
- Chemoreceptors: Sensitive to chemicals.
- Mechanoreceptors: Sensitive to mechanical stimuli.
- Photoreceptors: Light-sensitive.
- Thermoreceptors: Sensitive to temperature variations.
- Nociceptors: Responsible for the sensation of pain.
Depending on Their Position
- Internal receptors: Responsible for collecting information inside the body.
- External receptors: Responsible
Cell Structures: Golgi, Lysosomes, Vacuoles, Ribosomes, Mitochondria
Golgi Apparatus
The Golgi apparatus is composed of flattened, sac-like units (cisternae) formed by smooth membranes. These cisternae are typically clustered in groups of 5 to 8, forming a stack called a dictyosome. At the edges of the cisternae, vesicles bud off, containing various cellular products. Dictyosomes have two faces: a forming face (cis) and a maturing face (trans), which leads to the corresponding vesicles.
Lysosomes
Lysosomes are characteristic of animal cells. They are membrane-bound,
Read MoreCharacteristics of Fish, Amphibians, Reptiles, Birds, and Mammals
Fish
Body Features
- Fusiform body.
- Fish limbs are fins. Most fish have: 2 pectoral fins, 2 pelvic fins, one caudal fin, one anal fin, and one or more dorsal fins. However, there are exceptions.
- Their body is covered with scales, which are overlapped. Sharks and rays have small denticles instead of flat scales.
- They have a sensory organ, the lateral line, which detects water vibrations.
- Most fish have a natatory bladder, an
Pulmonary and Plant Respiration, Animal and Plant Excretion
Pulmonary Respiration
In pulmonary respiration, gas exchange is performed in the lungs. The lungs are connected to the outside through the mouth and nostrils, and continue via the pharynx, larynx, trachea, and bronchi. This type of respiration occurs in vertebrates: amphibians, reptiles, birds, and mammals.
Evolution of the Pulmonary Respiratory System
- Increasing the area of gas exchange (e.g., amphibians).
- Acquisition of ventilation mechanisms. In reptiles, birds, and mammals, the process of air entering