Comprehensive Notes on Biodiversity and the Domains of Life

Biodiversity and Domains of Life

Biodiversity

Biodiversity, or biological diversity, refers to the variety of life on Earth.
It encompasses living organisms, their genetic differences, and the ecosystems they inhabit.
Approximately 1.8 million species have been identified.
Estimates suggest that the total number of species ranges from 5 to 30 million.

Types of Biodiversity

Species diversity: The variety of different types of species in a particular area, ranging from plants to microorganisms.
Genetic diversity: Variations in the genetic resources of organisms, with each individual differing in their genetic makeup.
Ecological diversity: The diversity among different ecosystems in a region, such as deserts, rainforests, oceans, and mountains.

Advantages of Biodiversity

Supports food security and livelihoods through genetic diversity in crops.
Ensures natural sustainability for all life forms.
Healthy ecosystems can withstand and recover from disasters.
Offers medicinal benefits and improves human health through outdoor environments, increasing life satisfaction and reducing blood pressure and anxiety.
A WWF report in 2020 indicated an average decline of 68% in global populations of mammals, fish, birds, reptiles, and amphibians since 1970.

Threats to Biodiversity

Human activities, such as population growth, land conversion, and habitat loss.
Commercial fishing and hunting can reduce species numbers and lead to extinction.
Overuse and high numbers of visitors can damage plant life and stress animal populations.
Pollution, including chemicals and nutrient loading, poses threats to aquatic and terrestrial species.

Massive Extinctions Due to Human Activity

The International Union for Conservation of Nature (IUCN) notes that many species are threatened with extinction.
Species at risk include:
- 1 out of 8 birds
- 1 out of 4 mammals
- 1 out of 4 conifers
- 1 out of 3 amphibians
- 6 out of 7 marine turtles
Other statistics:
- 75% of genetic diversity of agricultural crops has been lost.
- 75% of the world’s fisheries are fully or overexploited.
- Up to 70% of the world’s known species risk extinction if global temperatures rise by more than $3.5°C$ .
- $1/3$ of reef-building corals are threatened with extinction.
- Over 350 million people suffer from severe water scarcity.

Conservation Efforts

Conservation efforts have made a significant difference in biodiversity.
Over 100,000 protected areas, including national parks and wildlife refuges, provide habitat for wildlife and help keep deforestation in check.

Species Dependence

Species depend on each other for survival, creating a balanced ecosystem.
Example: In an agricultural field:
- Crop byproducts feed cattle.
- Cattle waste enriches the soil, nourishing crops.
- Crops yield grain and straw.
- Straw provides organic matter and fodder.
- Crops are food sources for humans and animals.
- Soil organisms benefit from crops.
- Bacteria break down cellulose fibers from straw, enriching the soil.
- Amoebas feed on bacteria, making lignite fibers available for plants.
- Algae provide organic matter and fix nitrogen.
- Rodents aerate the soil and improve water-holding capacity.
- Insects grind organic matter, leaving enriched droppings.
- Earthworms contribute to soil fertility by providing aeration, drainage, and maintaining soil structure.
Industrial farming techniques can disrupt this biodiversity by depriving species of food and introducing chemicals, destroying the soil's fertility.

Ecosystems

Ecosystem diversity refers to the diversity of habitats, ecological communities, and ecological processes in the biosphere, as well as differences within individual ecosystems.

Domains and Kingdoms of Organisms

All living organisms can be classified into three domains: Archaea, Bacteria, and Eukarya.
These domains are further divided into six kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia.

Prokaryotes vs. Eukaryotes

Living organisms are divided into prokaryotes and eukaryotes based on cell structure.
Prokaryotic cells lack a nucleus.
Eukaryotic cells have a nucleus and other organelles.

Basic Terms

Nutrition: Autotrophic (makes its own food) or heterotrophic (feeds on other living things).
Cell organization: Unicellular (one cell) or multicellular (two or more cells).
Cell type: Eukaryotes (genetic material surrounded by a membrane) or prokaryotes (lacking a membrane).
Respiration: Aerobic (needs oxygen) or anaerobic (does not use oxygen).
Reproduction: Sexual, asexual, or through spores.
Movement: Self-moving or static.

Kingdoms

Animalia: Multicellular, heterotrophic eukaryotes with aerobic respiration, sexual reproduction, and movement.
Plantae: Immobile, autotrophic, multicellular, and eukaryotic organisms containing cellulose and chlorophyll, essential for oxygen production through photosynthesis; reproduce sexually or asexually.
Fungi: Unicellular (yeast and molds) and multicellular (mushrooms) organisms that are not capable of photosynthesis; they decompose organic matter and acquire nutrients through absorption, having chitin in their cell walls and reproducing through spores.
Protista: Eukaryotic organisms that are not animals, plants, or fungi; they have diverse characteristics and may resemble animals, plants, or fungi.
Monera: Microscopic living things, including prokaryotes (Archaea and Eubacteria), present in all habitats, composed of single-celled organisms without a defined nucleus; bacteria are aerobic and heterotrophic, while archaea are usually anaerobic and chemosynthetic.

Archaebacteria

Cell wall composition allows them to live in extreme environments like hot springs and hydrothermal vents.
Methanogens are found in the guts of animals and humans.
They reproduce by binary fission (asexual reproduction), have one circular chromosome, and use flagella to move.

Eubacteria

Considered true bacteria and live in almost every type of environment.
Many are associated with disease, but most do not cause disease.
They compose the human microbiota and ensure normal bodily functions.

Human Microbiota

The human body is inhabited by millions of tiny living organisms (bacteria, fungi, viruses) called the human microbiota.
Bacteria are found on the skin, in the nose, mouth, and especially in the gut.
Acquired during birth and the first years of life, they live with us throughout our lives.
Involved in healthy growth, protecting the body from invaders, helping digestion, and regulating moods.
Changes in the microbiota may occur depending on diet, environment, interactions with people and animals, and medicines taken.

Microbiota and Health

Disruption of microbiota (dysbiosis) can trigger ailments like obesity, irritable bowel syndrome, dermatitis, and neurological imbalance.
Probiotics and prebiotics can adjust microbial imbalance.

Effects of Gut Bacteria

Can increase the occurrence of obesity, mental disorders (depression, anxiety, and autism), and gut disorders (Irritable Bowel Syndrome, Crohn’s, ulcerative colitis, etc.), autoimmune disorders (rheumatoid arthritis), and more.
Babies delivered via Cesarean section are more likely to be overweight or obese as adults.

Microbiota Functions

Skin: Protects against opportunistic bacteria and pathogens; helps in healing wounds, fortifying the immune system, and producing signaling molecules.
Gut: Digests complex carbohydrates, extracts nutrients, produces vitamins K2 and B12, hormones, neurotransmitters, and metabolites.
Short-chain fatty acids derived from the microbiome are part of our normal development process.

Acquisition of Microbiota

Babies get microorganisms from their moms during vaginal delivery or from contact with the mom’s skin after cesarean delivery.
Breastfeeding helps babies acquire bacteria from the mother’s skin that colonize the baby’s intestines.
As babies grow, they get microorganisms from solid food, crawling on the floor, and putting their hands in their mouths.