- 1 Genetics
- 2 Biology
- 3 Animals
- 4 Theoretical zoology
- 5 Zoography
- 6 Vertebrate Zoology
- 7 Mammalogy
- 8 Ornithology
- 9 Dinosaurology
- 10 Herpetology
- 11 Ophiology
- 12 Batrachology
- 13 Ichthyology
- 14 Invertebrate Zoology
- 15 Echinodermology
- 16 Entomology
- 17 Lepidopterology
- 18 Arachnology
- 19 Parasitology
- 20 Systematics & Taxonomy
- 21 Hypotheses
- 22 See also
- 23 References
- 24 External links
Zoology is a biological science that pertains to animals.
Genetics is the study of the genes, how they affect organisms, and how they are passed from one generation to the next. A scientist that studies genetics is called a geneticist.
DNA, deoxyribonucleic acid, is a molecule found in almost every cell of every body of every organism. DNA contains genes, which are the basic instruction codes for making and running a living organism. Strands of DNA make up chromosomes. (Chromosomes are made of DNA, which is made up of genes.)
Genes, through DNA and chromosomes, are passed from one generation to the next by inheritance. Because of this, offspring resemble their parents. Through mixing and occasional mutation, genes can change. When genes change, how the organism forms and how it works may be changed.
How all these changes affect individuals, populations, and entire species is the work of geneticists. ______
"A recent comparison of the draft sequences of mouse and human genomes has shed light on the selective forces that have predominated in their recent evolutionary histories. In particular, mouse-specific clusters of homologues associated with roles in reproduction, immunity and host defence appear to be under diversifying positive selective pressure, as indicated by high ratios of non-synonymous to synonymous substitution rates. These clusters are also frequently punctuated by homologous pseudogenes. They thus have experienced numerous gene death, as well as gene birth, events. These regions appear, therefore, to have borne the brunt of adaptive evolution that underlies physiological and behavioural innovation in mice. We predict that the availability of numerous animal genomes will give rise to a new field of genome zoology in which differences in animal physiology and ethology are illuminated by the study of genomic sequence variations."
Def. the "study of all life or living matter" is called biology.
On the right is a drawing of the archaean Haloquadratum walsbyi.
As the study of biology is the study of all living organisms, zoology is a specialty of biology. All zoologists are also considered biologists.
Other branches of biology include botany (the study of plants), mycology (the study of fungi), phycology (the study of algae), and virology (the study of viruses).
The biological definition of animals includes all members of the kingdom Animalia.
Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, and unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which are autotrophs, producing their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With very few exceptions, animals breathe oxygen and respire aerobically. All animals are motile (able to spontaneously move their bodies) during at least part of their life cycle, but some animals, such as sponges, corals, mussels, and barnacles, later become sessile. The blastula is a stage in embryogenesis, embryonic development, that is unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a relatively flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible. This may be calcified, forming structures such as an exoskeleton of shells, bones, and spicules. In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi) are held in place by cell walls, and so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, and desmosomes.
With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues. These include muscles, which enable locomotion, and nerve tissues, which transmit signals and coordinate the body. Typically, there is also an internal digestive chamber with either one opening (as in flatworms) or two openings (as in deuterostomes).
Nearly all animals make use of some form of sexual reproduction. They produce haploid gametes by meiosis; the smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm, also develops between them. These germ layers then differentiate to form tissues and organs.
Repeated instances of inbreeding, mating with a close relative, during sexual reproduction generally leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for inbreeding avoidance, or avoiding close inbreeding. In some species, such as the splendid fairywren (Malurus splendens), females benefit by mating with multiple males, thus producing more offspring of higher genetic quality.
Some animals are capable of asexual reproduction, which often results in a genetic clone of the parent. This may take place through fragmentation; budding, such as in Hydra and other cnidarians; or parthenogenesis, where fertile eggs are produced without mating, such as in aphids.
Animals are categorised into ecological groups depending on how they obtain or consume organic material, including carnivores, herbivores, omnivores, detritivores, and parasites. Interactions between animals form complex food webs. In carnivorous or omnivorous species, predation is a consumer-resource interaction where a predator feeds on another organism (called its prey). Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various anti-predator adaptations. Almost all multicellular predators are animals. Some consumers use multiple methods; for example, in parasitoid wasps, the larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Other animals may have very specific feeding behaviours, such as hawksbill sea turtles that primarily eat sponges.
Most animals rely on the energy produced by plants through photosynthesis. Herbivores eat plant material directly, while carnivores, and other animals on higher trophic levels, typically acquire energy (in the form of reduced carbon) by eating other animals. The carbohydrates, lipids, proteins, and other biomolecules are broken down to allow the animal to grow and to sustain biological processes such as locomotion. Animals living close to hydrothermal vents and cold seeps on the dark sea floor do not depend on the energy of sunlight. Rather, archaea and bacteria in these locations produce organic matter through chemosynthesis (by oxidizing inorganic compounds, such as methane) and form the base of the local food web.
Animals originally evolved in the sea. Lineages of arthropods colonised land around the same time as land plants, probably between 510–471 million years ago during the Late Cambrian or Early Ordovician. Vertebrates such as the Sarcopterygii, lobe-finned fish, Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Animals occupy virtually all of earth's habitats and microhabitats, including salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of animals, plants, fungi and rocks. Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F). Only very few species of animals (mostly nematodes) inhabit the most extreme cold deserts of continental Antarctica.
Def. "that part of biology which relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct" is called zoology.
Zoography is descriptive zoology. Animals are described in comparison with other organisms, and their surroundings. This comparison takes into account variation among individuals and populations, and organizes it into systems and classifications that are used for making predictions, such as the evolutionary relationships among organisms.
The branches of zoology focusing on a particular taxonomic group (mammals, etc.) are often considered part of zoography.
Vertebrate zoology is the study of vertebrates, the animals that have a spinal column. This covers only about 3% of all known species.
Def. the "study of mammals" is called mammalogy.
Scientists who study mammalogy are called mammalogists.
Mammals are endothermic vertebrates that have fur or hair and feed milk to their young. Milk is a fluid produced by mammary glands.
There are about 5000 species of living mammal known to science. Mammals live in every habitat on Earth. They range in size from the Etruscan shrew (Suncus etruscus), the smallest living mammal, to the blue whale (Balaenoptera musculus) which is the largest animal to have ever lived. Humans (Homo sapiens) are also mammals. They are placed in the taxonomic class Mammalia.
- [American Society of Mammalogists]
- [Mammalian Species] a journal that consists of species accounts of mammals from around the world.
Def. "the scientific study of birds" is called ornithology.
Scientists who study ornithology are called ornithologists.
Birds are endothermic vertebrates that have feathers and lay eggs. Birds are considered the only living direct descendants of dinosaurs. They belong to the taxonomic class Aves.
There are about 10,000 species of living bird known to science. Birds live in every habitat on Earth. They range in size from the Bee Hummingbird (Mellisuga helenae), the smallest living bird, to the Common Ostrich (Struthio camelus), which standing up to 8 feet (2.4 m) tall, is the tallest living bird.
- [Avibase] a world bird database.
Def. "branch of paleontology that focuses on studying dinosaurs" is called dinosaurology.
Usually allied with geology rather than biology, paleontology is the study of past life. Dinosaurology is the specific branch of paleontology that is the study of dinosaurs. Because birds are the living descendants of dinosaurs, ornithology might be considered a branch of dinosaurology.
Scientists who study dinosaurs are usually called paleontologists, but might also be called dinosaurologists.
The non-avian dinosaurs lived during the Mesozoic Era, the time period between roughly 252 and 65 million years ago. The first dinosaurs evolved about 225 million years ago, and all but the birds became extinct by the end of the Mesozoic Era.
Dinosaurologists, like other paleontologists need a good grounding in geology and anatomy, as well as whatever other fields their particular study may involve.
Def. the "branch of biology dealing with reptiles (Reptilia) and amphibians" is called herpetology.
Scientists who study herpetology are called herpetologists.
Reptiles and amphibians are ectothermic vertebrates that have scales or naked skin. Reptiles lay shelled eggs or give birth to live young. Amphibians lay eggs without shells.
There are about 8000 species of living amphibian known to science, and more than 10,000 species of reptile.
Amphibians live in every terrestrial habitat on Earth except in the arctic and antarctic. Amphibians are also absent from marine environments. The amphibians comprise the taxonomic class Amphibia. The living amphibians include frogs and toads, salamanders and newts, and caecilians.
Reptiles also live in every terrestrial habitat on Earth except the artic and antarctic, but some species also occur in marine environments. Reptiles comprise the taxonomic class Reptilia. The living reptiles include lizards, snakes, tuataras, crocodilians, and turtles.
Def. the "study of snakes"is called ophiology.
Ophiology is a specialization of herpetology. Scientists who study ophiology are called herpetologists.
The name of this specialty comes from the Greek word for snake, ophis.
Def. the "study of amphibians" is called batrachology.
Batrachology is a specialty within herpetology. Scientists who study Batrachology are called herpetologists.
The name of this specialty comes from the Ancient Greek word for frog, batrakhos.
Def. "the study of fish" is called ichthyology.
Scientists who study ichthyology are called ichthyologists.
Fishes are endothermic vertebrates that live in the fresh or marine water.
Living species are extremely diverse, and belong to three taxonomic groups, Superclass Agnatha (jawless fishes), Class Chondrichthyes (sharks and rays), and the Osteichthyes (the bony fishes).
There are about 30,000 species of living fish known to science. Fish live in every aquatic habitat on Earth.
About the Photo: Considered a "living fossil" because it is an ancient class of lobe-limbed fish that otherwise went extinct more than 70 million years ago, the first living coelacanth was caught off the east coast of South Africa near the Chalumna River in 1938. Today, at least two major populations of coelacanths are known: one off east Africa, and another near Indonesia. Coelacanths cannot be eaten; their flesh contains an oil that is highly distasteful to human beings. This specimen in the image above weighs 160 pounds (72.6 kg) and measures 5.5 feet (1.67 m) in length.
See also: Fish
Invertebrate zoology is the study of animals that lack a spinal column. This covers approximately 97% of all known living species.
Def. study of the echinoderms is called echinodermology.
Echinodermology is a specialty of invertebrate zoology that studies echinoderms. The echinoderms include sea stars, urchins, and crinoids. All species are marine, so this is also a specialty of marine biology. Scientists who study echinoderms most often are called either marine biologists or invertebrate zoologists.
Entomology is the study of insects. Scientists who study entomology are called entomologists.
Def. the "scientific study of butterflies and moths" is called lepidopterology.
On the right is an example of Callioratis grandis from Mulanje Mountain, Africa.
Lepidopterology is the study of the Lepidoptera, the group of insects that includes butterflies and moths. It is a specialty of entomology, which is the overall study of insects. Most scientists who study the lepidoptera consider themselves to be entomologists.
Arachnology is the study of spiders, scorpions, and related arthropods. Scientists who study arachnology are called arachnologists.
Def. the "study of the spider, a branch of arachnology" is called araneology.
The "Acanthocephala, are descended from, and should be considered as, highly modified rotifers. Genetic research has determined this is unequivocal; the Acanthocephalans are modified rotifers". ______________
Parasitology is the study of parasites. In this context, a parasite is usually an invertebrate, and as such parasitology is a specialization of invertebrate zoology. Scientists that study parasites are called parasitologists.
Parasites are organisms that live on or in, and take their nutrition from, another living organism called a host. Rarely do parasites kill their hosts, since finding a new host can be quite difficult. Individual parasites may do little harm to their host, but large numbers of them can cause great problems. This kind of relationship where one organism lives off another giving either nothing in return or causing harm is called parasitism.
Parasites may be found in many invertebrate taxonomic groups. Commonly encountered parasites include tapeworms, roundworms, and lice.
Systematics & Taxonomy
Systematics is the study of the evolutionary relationships among organisms. It includes taxonomy, which is the study of the names of organisms and their organization into categories. Scientists who study systematics are called systematists, while taxonomists primarily study taxonomy. Most systematists are also taxonomists.
Living organisms are grouped into a hierarchy of categories. The main categories are Kingdom (or Regnum, pl. Regna), Phylum (pl. Phyla), Class, Order, Family, Genus (pl. Genera), and Species (pl. Species). Every living organism is classified into one, and only one, of each of those categories. There are additional categories used for some groups, but not all.
The classification of organisms can change as more is learned about the living world around us.
Below are two ideas of how life may be divided into Kingdoms (Regna).
- Four Regna listed by Whittaker & Margulis (1978): Animalia - Plantae - Fungi - Protista
- Five Regna listed Cavalier-Smith (1981): Animalia - Plantae - Fungi - Chromista - Protozoa
Below is one recent list of the Phyla of within the Kingdom Animalia. Note number 8, Chordata. That is the Phylum that includes vertebrates, the animals with a spinal column that includes humans.
Regnum: Animalia Phyla (36):
An hypothesis is a scientific statement made to explain some part of the world. It is not a guess. It is testable by scientific means, and is falsifiable (able to be disproved) by those means. Coming up with hypotheses and testing them are the main occupation of science.
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