Marine and Freshwater Ecosystems: Zones, Biodiversity and Trophic Levels

Marine Zones and Their Characteristics

Littoral Zone: Influenced by temperature, waves, tides, salinity, sunlight and substrate. Species population: small crustaceans, barnacles, sea urchins and algae.

Neritic Zone: The region of the sea where there is the greatest amount of life. It is the richest in benthic creatures and beings that depend on light, such as photophilic algae. It is the most commercially important sea area. Species population: huge shoals of algae, corals and fish.

Pelagic Zone: The region away from the coast, which includes the open ocean. Fish that live in the ocean are important to commercial fishing. The pelagic zone includes the territorial waters and all international waters. Species population: fish, dolphins, ocean mammals, whales and others.

There is practically no benthic life in the bathyal zone, due to the difficulty of fixation on the escarpments, which makes the ground unstable. There is a scarcity of species in general. Large populations of fish species (carnivores) are found there.

The abyssal zone encompasses the abyssal plains, which are extensive, and outcrops of hydrothermal vents with methane sources. There is no plant life in the abyssal plains. This zone covers 92% of the ocean floor. Its fish inhabitants are species resistant to high pressure, which have bioluminescence and a bizarre, sensitive vision.

The hadal zone is the deepest region, characterized by cold, complete darkness, overwhelming pressure and a scarcity of food resources. Its inhabitants are species of bacteria.

Cell Structure and Cellular Processes

All living things, unless they are viruses, are composed of cells: prokaryotic cells and eukaryotic cells.

Metabolism is the set of chemical transformation activities that occur inside a living cell. Anabolism is the synthesis of substances, while catabolism is the breakdown of substances.

All living beings reproduce for the perpetuation of their species, through asexual reproduction and sexual reproduction.

The Biosphere and Levels of Organization

The biosphere is composed of the surface of the earth (A), the bottom of the atmosphere (B), reaching to the bottom of the oceans (C). The biosphere is the set of all the ecosystems http://www.sobiologia.com.br/conteudos/Ecologia/Ecologia3.php of the Earth.

Species: two or more organisms of the same kind are considered a species when they can reproduce with each other, giving rise to fertile offspring.
Populations: consist of organisms of the same species, that is, a group of individuals that reproduce among themselves.
Communities: include all the populations that occupy a particular area.
Ecosystem: formed by the community and its living environment.

The community is divided into living biotic components. The set of components that do not live, such as rainfall regime, temperature, light, humidity and soil minerals, is called abiotic components.

Ecosystems: in a particular place, whether it is a closed vegetation, bordering vegetation, caatinga, Atlantic forest or Amazon forest, all the relations between organisms with each other and with their environment, or any other denomination, are all the relations between biotic and abiotic factors in a certain area, called an ecosystem.

Habitat: the place where one or more species live. For example, the maned wolf's habitat is the cerrado.

Ecological niche: the unit of distribution of each kind (each group of organisms is peculiar in obtaining its energy within its habitat).

The Ecosphere and Trophic Relationships

Ecosphere or Biosphere: The earth is composed of several ecosystems, whether aquatic, terrestrial or air. The sum of all these ecosystems is called the biosphere. Therefore, the biosphere is the space where life occurs and the part of the planet on which life acts and has power.

Producers: organisms capable of photosynthesis or chemosynthesis. They produce and accumulate, through biochemical processes, energy used as food from water, carbon dioxide and light. In aphotic environments (without light), producers also exist.

Primary consumers: animals that feed on producers, that is, herbivorous species. They can be primary consumers ranging from microscopic planktonic larvae or benthic invertebrate grazers (from the bottom) to large terrestrial mammals such as elephants and giraffes.

Secondary consumers: animals that feed on herbivores, the first category of carnivorous animals.
Tertiary consumers: large predators such as orcas and lions, which capture large prey, being considered predators at the top of the food chain. They usually have large population sizes and lower densities.

Decomposers: responsible for the decomposition of organic matter, turning it into nutrients and minerals that become available again in the environment. Decomposers are represented by bacteria and fungi, and are the last link in the food chain or web, closing the cycle.

Omnivores: feed on everything.

Trophic Levels: the set of individuals that obtain nutrients in the same way, placed at the same trophic level.

• Producers occupy the first trophic level.
• Primary consumers, which feed on producers, are herbivores and constitute the second trophic level.
• Secondary consumers, which are carnivores, constitute the third trophic level. After these come the fourth trophic level, and so on.
• Decomposers always occupy the last level, forming an energy transfer panel that degrades both consumers and producers.

Food Chains and Food Webs: A food chain does not show the complex relations between trophic levels in an ecosystem. For this reason, the concept of the food web is used, which represents a true situation in an ecosystem found, that is, several chains simultaneously intertwined and occurring.

Biodiversity and Specific Environments

The term biodiversity, or biological diversity, describes the wealth and variety of the natural world. Plants, microorganisms and animals provide food, medicines and good raw materials consumed by humans.

This occurs in the biocycle of marine environments, or thalassocycle.

Mangroves are a coastal ecosystem of transition between terrestrial and marine environments. Characteristic of tropical and subtropical regions, it is subject to the tidal regime and dominated by typical plant species, with which other plants and animals are associated. The biological richness of these coastal ecosystems makes them natural "nurseries" for both the species of these environments and for fish and other animals that migrate to coastal areas during at least one phase of their life cycle.

Life in Rivers and Lakes: The Limnocycle

The freshwater environment is constituted by large continental projections: rivers, lakes and swamps. Depending on the speed of the water, these are classified as lentic (lakes and lagoons) and lotic (streams, rivers and rapids).

The limnocycle includes lotic waters (rivers, streams and rapids) and lentic waters (lakes and lagoons).