Species, Ecosystems, and Biological Interactions
Species, Population, and Community
Species: A set of individuals similar to each other and their parents, capable of reproducing and producing fertile offspring.
Population: The total number of individuals of the same species inhabiting a given territory.
Community: Also known as a biocenosis, it is a group of populations of different species living in a specific area.
Ecosystem: Biotic and Abiotic Factors
Ecosystem: The set of populations that make up a community, plus their physical environment, i.e., the relationship between the biotope and the biocenosis.
Biotic factors: The influences that an organism receives from others of the same or different species.
Abiotic factors: The influences that the physicochemical characteristics of the environment exert on organisms (e.g., light, temperature, salinity).
Trophic Structure
Trophic level refers to how organisms obtain matter and energy.
- Producers: Autotrophs that utilize light energy and, through photosynthesis, synthesize organic matter from inorganic matter. This level consists of green plants.
- Primary Consumers: Heterotrophs that utilize the chemical energy stored in organic matter produced by producers. This level comprises herbivores.
- Secondary Consumers: Heterotrophs that feed on primary consumers. This level is composed of carnivores.
- Decomposers: Feed on organic remains of organisms from previous trophic levels, converting organic matter into inorganic matter. This level comprises bacteria and fungi.
- Transformers: Transform inorganic substances into forms usable by producers. This level includes some types of bacteria.
Intraspecific Relationships
Intraspecific relationships involve interactions between individuals of the same population. Different types of associations can occur:
- Family: Formed by closely related individuals for procreation and parental care.
- Colonial: Comprised of individuals originating from a single parent and physically attached to each other.
- Gregarious: Individuals aggregate to achieve a specific purpose, such as foraging, defense, reproduction, or migration.
- State: Individuals constitute genuine societies with a hierarchy and division of labor.
Interspecific Relationships
In a biotope, multiple species of animals and plants coexist, interacting and influencing each other. Relationships can be temporary or permanent, beneficial, harmful, or neutral. Types of interspecific relationships include:
- Mutualism and Symbiosis: Both species benefit from the relationship.
- Commensalism: One individual benefits without harming or benefiting the other.
- Inquilinism: One animal shelters another for protection without causing harm or deriving any food benefit.
- Antibiosis: One species is harmed by another, while the latter receives no benefit. For example, some plants are harmful when ingested by animals, or poisonous mushrooms.
- Parasitism: One individual (the host) is harmed, while the other (the parasite) benefits.
- Predation: One individual (the predator) kills and devours another (the prey) for food.
- Competition: Two species compete for a common resource.
DNA Replication
The DNA molecule contains all the information that determines the characteristics of a cell. When a cell divides by mitosis, it distributes this information between the two daughter cells. To do so accurately, the information must be replicated. DNA replication is semiconservative because the DNA double helix separates like a zipper, and free nucleotides in the nucleus occupy the spaces on both strands, considering base complementarity. At the end of the process, two identical DNA molecules are formed, each with one original and one new strand. Thus, the information is replicated and passed on to each daughter cell.