Biodiversity and Classification of Living Things
Biodiversity
What is Biodiversity?
It is the totality of species and ecosystems of a region, including the entire gene pool.
Morphological Adaptations
These are anatomical structures that ensure an organism’s harmonious relationship with its environment.
Physiological Adaptations and Types
These are changes in individual organ function, enabling better environmental adaptation. Types include body temperature regulation and fruit ripening.
Convergent Evolution
Different groups of animals or plants develop similar structures in response to similar environmental pressures.
Adaptive Convergence
Different groups of organisms develop similar adaptations.
Divergence
Species within the same group adapt to different lifestyles.
Adaptive Radiation
The evolution of a single ancestral species giving rise to species differing in body parts.
Co-evolution
Evolution resulting from interactions between interdependent species, where one adaptation leads to another.
Levels of Biodiversity
There are three main levels: genes, species, and ecosystems.
Genetic Diversity
The variation of genes within a species.
Species Diversity
The total number of species in a given region.
Ecosystem Diversity
The diverse coping mechanisms enabling life’s diversification across terrestrial habitats.
Extinct Species
Represents the disappearance of flora and fauna species.
Endangered Species
Species whose population range has dramatically decreased.
Threatened Species
Species in danger of disappearing in the medium term.
Rare Species
Species that are naturally rare, highly sensitive to human presence, and tend to decline rapidly.
Classification of Living Things
Early Classification Attempts
Primitive humans classified plants and animals as dangerous/safe or edible/inedible. In the fifth century, Aristotle and his followers classified approximately 1000 known species. They used a “top-level” classification of plants and animals, with “second-tier” subdivisions (e.g., plants were divided into trees, shrubs, and herbs). Criteria included extrinsic factors (presence/absence of red blood) and intrinsic factors (number of legs, presence/absence of eggs).
Red-blooded animals (vertebrates): Subgroups included four-legged creatures, egg-laying animals, feathered bipeds, etc.
Red-bloodless animals (invertebrates): Subgroups included cephalopods, crustaceans, mollusks, echinoderms, and insects.
This classification persisted for over 1000 years. Medieval bestiaries contained inaccurate animal information. In the sixteenth century, Konrad von Gesner published “Historia Animalium.”
Binomial Nomenclature and its Characteristics
A system assigning two names to each species. Characteristics include:
- Species as the fundamental taxonomic unit.
- A scientific name in Latin or Latinized Greek (genus and specific epithet).
- Facilitates broader species grouping in taxonomic categories.
- Uses uniform scientific terminology.
Systematics
The branch of biology studying life’s diversity and phylogenetic relationships. It’s a comprehensive field of biological study.
The Scheme of Life Forms
Closely related species are grouped into genera, genera into families, families into orders, orders into classes, classes into phyla, and phyla into kingdoms.
Modern Classification of Living Things
Ernst Haeckel initially proposed three kingdoms: animal, plant, and protist. Robert H. Whittaker (1959) proposed five: Monera, Protista, Fungi, Animalia, and Plantae. Advances in biochemistry, genetics, and molecular biology led to a seven-kingdom system: two prokaryotic (Bacteria and Archaea) and five eukaryotic (Protozoa, Chromista, Plantae, Animalia, and Fungi). Red and green algae remain challenging to classify within Chromista or Plantae.
Classes within Each Kingdom
- Archaebacteria: Extreme halophiles, methanogens, thermoacidophiles
- Eubacteria: Heterotrophs, autotrophs, chemotrophs
- Protozoa: Archamoeba, diplomonads, kinetoplastids, euglenids
- Chromista: Oomycota, Bacillariophyta, Chrysophyta, Xanthophyta, Phaeophyta
- Red and Green Algae: Rhodophyta (red algae), Chlorophyta (green algae)
- Fungi: Chytridiomycota, Zygomycota, Basidiomycota, Deuteromycota, Ascomycota
- Plants:
- Non-vascular plants: Bryophyta, Hepatophyta, Anthocerotophyta
- Vascular plants:
- Seedless: Psilophyta, Lycopodiopsida, Sphenophyta, Pteridopsida
- With seeds:
- Gymnosperms: Coniferophyta, Cycadophyta, Gnetophyta
- Angiosperms: Anthophyta
- Animals: Divided into vertebrates and invertebrates. Invertebrates are further divided into various phyla (e.g., Rotifera, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata). Chordates are divided into three subphyla (Urochordata, Cephalochordata, Vertebrata), with Vertebrata further divided into seven classes (Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia).