Hominid Evolution: From Africa to Homo Ergaster
The Hominids: An Evolutionary Overview
The hominids are a group of non-arboreal primates whose origin is in Africa for at least several million years. A key characteristic is moving into a bipedal position. This conditions the situation of the foramen magnum at the base of the skull, through which the spinal cord passes to the backbone. On each side and downward facing are the occipital condyles: the double articulation of the skull to the backbone. Their palate is U-shaped, surrounded with a dental
Read MorePlant Physiology: Relationships and Reproduction
Plant Relationships and Stimuli Responses
Plants can receive and transmit stimuli from the external environment and have the capacity for movement. The regulation of a plant’s physiological activities depends on many internal and external factors. Internal factors are mainly plant hormones or phytohormones, while external factors include the length of day and night.
Plant Hormones
A hormone is a chemical produced by specialized cells, which acts on other cells of the individual, away from the hormone’
Read MorePhotosynthesis and Chemosynthesis: Energy Conversion in Organisms
Light Phase (Photochemical)
Photosynthetic pigments are associated with membrane proteins, constituting photosystems. By absorbing a photon, the pigment is ionized (oxidized). The pigment acts as an electron donor to a molecule called an electron acceptor. Then, a series of electron acceptors are reduced and successively oxidized, forming a transport chain. During this process, energy is released, which is harnessed by ATP synthases to produce ATP via the chemiosmotic hypothesis (proton accumulation
Read MoreUnderstanding Genetics, Human Genome, and Neurons
Nature Genetics
Genetics is the science that studies the mechanisms of heredity, as the traits passed from parent to child. The basic units of heredity are the genes that allow the continuity of species and determine that each individual has some distinctive features, unique and unrepeatable.
Each cell in the body contains 23 pairs of chromosomes, structures that are composed of DNA and determine your genotype or genetic inheritance. There are 22 pairs of chromosomes, not related to sex, and another
Read MorePlant Epidermis: Deposits, Cells, and Trichome Secretion
Plant Epidermis: Deposits, Cells, and Secretion Mechanisms
Cuticular and Epidermal Deposits
In epidermal cells, various salt deposits manifest as crystals. These deposits are located both on the cuticle surface and permeating it, even within the cell wall itself. Many plants exhibit significant mineralization of the cell wall, with silica joining other salt deposits. These salts distribute evenly between cellulose and cutin. Calcium carbonate mineralization appears coarser than silica, with a granular
Darwin, Lamarck, and Neo-Darwinism: Evolution Theories
Darwin’s Theory of Evolution
Darwin’s theory posits that populations evolve over time through a process of natural selection. Key points include:
- Organisms produce more offspring than can survive.
- Despite overpopulation, population sizes generally remain constant.
- This leads to a struggle for resources (food, space).
- Individuals within a species vary in their traits (some are more “fit”).
- The fittest individuals are more likely to survive and reproduce.
Conclusions of Darwin’s Theory
- Individuals with traits