The following characteristics generally distinguish living organisms from non-living units of matter: cellular; awareness; consumption; regulation; adaptation; development; and reproduction (CAC-RADAR)
Awareness: Living organisms are aware of their environment and respond to stimuli through sensory mechanisms. Note that higher levels of integrated sensory awareness leads to degrees of consciousness.
Regulation: Living organisms maintain internal stability through a regulatory process called homeostasis. This involves regulating internal conditions, such as temperature, pH, and nutrient levels, within a narrow range to support proper functioning.
Adaptation: Living organisms adapt to their environment over time through instincts or learning.
Variation: Random variation occurs due to genetic mutations, genetic recombination, reproduction, environmental factors, and other random reasons.
Inheritance: Offspring inherit traits from parents via genetic code recombination.
Reproduction. Those who survive, can reproduce.
Adaptation. Over time, natural selection leads to environmental adaptation.
Domain: The first level. There are three domains: Archaea, Bacteria, and Eukarya. Archaea and Bacteria contain prokaryotic organisms, while Eukarya includes organisms with eukaryotic cells.
Kingdom: The second level of classification. The major kingdoms include Animalia (animals), Plantae (plants), Fungi (fungi), Protista (protists), Archaea (archaea), and Bacteria (bacteria).
Phylum (in animals) or Division (in plants): The third level of classification. Phyla are used to classify animals, while divisions are used for plants. They group organisms based on common characteristics and body plans.
Class: The fourth level of classification. Classes further categorize organisms within a phylum or division based on shared characteristics.
Order: The fifth level of classification. Orders classify organisms within a class, and represent more specific groupings based on similarities.
Family: The sixth level of classification. Families group related organisms within an order that share even more specific characteristics.
Genus: The seventh level of classification. Genera (plural of genus) classify organisms within an order based on more specific shared traits.
Species: The most specific level of classification. Species is the lowest and most specific rank in the taxonomic hierarchy. It refers to a group of organisms that share common characteristics, and that can interbreed to produce fertile offspring.
The hierarchy above allows scientists to organize and classify the immense diversity of life on Earth, providing a framework for understanding evolutionary relationships and biodiversity.
1. Archaea is the domain of single-celled prokaryotic (non-nuclei in cell)microorganisms that often thrive in extreme environments, such as hot springs, salt flats, and deep-sea hydrothermal vents. This domain emerged on planet Earth approximately 3.8 billion years ago. Note that the planet was formed about 4.5 billion years ago from gravitational debris generated by the explosion of a star (a "supernova" event as star explosions are called) that occurred about 5 billion years ago.
2. Bacteria correspond to another domain of single-celled prokaryotic (non-nuclei in cell) organisms emerging on planet Earth about 3.5 billion years ago. Bacteria are widespread and found in diverse habitats, including soil, water, and the bodies of plants and animals. Bacteria exhibit remarkable metabolic diversity, and play essential roles in ecological processes such as decomposition, nutrient cycling, and symbiotic relationships.
Monera Kingdom. This kingdom was the first to emerge on Earth about 3.8 billion years ago, and includes ingle-celled prokaryotic (non-nuclei in cell) like archaea and bacteria domains.
Protista Kingdom: Protists emerged around 2 billion years ago. Protists are eukaryotic (nucleus-containing cell) microorganisms and are mostly unicellular, but can also be multicellular. Protists include organisms such as amoebas, paramecia, algae, and protozoans.
Fungi Kingdom: Fungi diverged from other eukaryotes around 1 billion years ago. Fungi include organisms such as mushrooms, molds, yeasts, and mildews. They are eukaryotic (i.e. cell has a nucleus surrounded by a membrane) and heterotrophic (i.e. cannot produce their own food). Fungi obtain nutrients by decomposing organic matter, or by forming symbiotic relationships with other organisms.
Animalia Kingdom: Animals emerged around 635 million years ago. Animals are multicellular organisms with complex tissues and organs. The "Cambrian Explosion" was a significant growth in animal population that occurred around 541 million years ago. Some argue that the animal population and diversity increase was due to an increase in levels of oxygen available, while others suggest that it was due to the evolutionary emergence of vision.
Kingdom: Animalia (animals)
The animal kingdom is a diverse group of organisms that includes a vast array of multicellular, eukaryotic (nuclei containing cell) organisms with many divisions called "phylums":
Porifera: Porifera are commonly known as sponges. They are simple, multicellular animals with porous bodies and no true tissues or organs.
Cnidaria: Cnidarians include organisms such as jellyfish, corals, and sea anemones. They have specialized stinging cells called cnidocytes and display radial symmetry. Cnidarians may exist in both polyp and medusa forms.
Platyhelminthes: Platyhelminthes includes flatworms, which are often flat and exhibit bilateral symmetry. This phylum includes organisms such as planarians, tapeworms, and flukes.
Nematoda: Nematodes, commonly known as roundworms, are unsegmented worms with cylindrical bodies. They are found in various habitats, including soil and aquatic environments, and some species can be parasitic.
Annelida: Annelids are segmented worms, and examples include earthworms and leeches. They possess repeated body segments and exhibit bilateral symmetry.
Arthropoda: Arthropods are the largest phylum in the animal kingdom, and includes insects, spiders, crustaceans, and many others. Arthropods have exoskeletons, jointed limbs, and segmented bodies.
Mollusca: Mollusks are soft-bodied animals with a muscular foot, often covered by a protective shell. Examples include snails, clams, squid, and octopuses.
Chordata: Chordates are characterized by the presence of a notochord, a dorsal nerve cord, and pharyngeal gill slits at some stage of their development. This phylum includes vertebrates such as fish, amphibians, reptiles, birds, and mammals.
Within each phylum, there are numerous classes, orders, families, genera, and species that further classify and categorize the diverse range of animals on Earth. Humans are part of the Chordate Phylum.
The Chordate Phylum
Notochord: The notochord is a flexible rod-like structure that runs along the length of the body. It provides support and serves as an attachment site for muscles. In some chordates, the notochord persists throughout the animal's life, while in others, it is replaced by the vertebral column (spine) during development.
Dorsal Nerve Cord: The dorsal nerve cord is a hollow, tubular structure located on the back (dorsal) side of the organism. It develops from a specialized ectodermal tissue called the neural tube. In chordates, the nerve cord is positioned dorsally and is responsible for transmitting nerve impulses, coordinating sensory and motor functions.
Pharyngeal Gill Slits: Chordates have pharyngeal gill slits, which are openings in the pharynx, or throat region. These slits are initially used for filter-feeding or respiration in aquatic chordates. In some groups, such as fish, the slits are retained throughout life for respiration, while in others, they may be modified for other functions, such as hearing or as components of the jaw and ear.
Post-anal Tail: Chordates possess a tail that extends beyond the anus. The post-anal tail provides locomotion and contributes to balance and propulsion in aquatic species. In many chordates, including humans, the tail disappears during embryonic development, although remnants can be observed in the coccyx (tailbone).
The chordate phylum includes a diverse range of organisms, from simple marine invertebrates to complex vertebrates. It encompasses various groups, including fish, amphibians, reptiles, birds, and mammals. Chordates have successfully adapted to different environments and display a wide array of anatomical, physiological, and behavioral adaptations. The phylum Chordata is of particular interest as it contains humans and other animals with remarkable evolutionary and ecological significance.
Mammals are a diverse group of animals belonging to the class Mammalia. They are characterized by several distinct features that set them apart from other animal groups.
Fur or Hair: Mammals have a covering of fur or hair on their bodies. This provides insulation, protection, and aids in sensory perception.
Mammary Glands: Mammals possess mammary glands that produce milk to nourish their young. Milk is typically provided to newborns through nursing.
Warm-Bloodedness: Mammals are warm-blooded animals, meaning they have the ability to regulate their body temperature internally. This enables them to thrive in diverse environments.
Internal Fertilization: Mammals reproduce through internal fertilization, where fertilization of eggs occurs within the body of the female.
Live Birth: Most mammals give birth to live offspring, as opposed to laying eggs. However, there are exceptions such as monotremes (platypus and echidnas), which lay eggs.
Diaphragm: Mammals have a muscular structure called the diaphragm, which aids in respiration by separating the chest and abdominal cavities.
Well-Developed Brains: Mammals generally possess well-developed brains and exhibit complex behaviors and social interactions.
Diverse Adaptations: Mammals have evolved to occupy various ecological niches, leading to a wide range of adaptations. Some are specialized for swimming (whales and dolphins), flying (bats), or life in trees (primates).
Mammals display tremendous diversity in size, habitat, diet, and behavior. The class Mammalia includes over 5,000 species, ranging from tiny shrews to massive whales, from burrowing rodents to soaring bats, and from grazing herbivores to predatory carnivores. Mammals inhabit nearly every habitat on Earth, including terrestrial, aquatic, and aerial environments. They play crucial ecological roles and have significant impacts on ecosystems and human societies.
Lemurs: Lemurs are primates found only on the island of Madagascar. They have a wide range of sizes and adaptations, including long tails and unique locomotion patterns.
Tarsiers: Tarsiers are small primates found in Southeast Asia. They have large eyes, long fingers, and are known for their exceptional leaping abilities.
New World Monkeys: This group includes monkeys found in Central and South America, such as capuchins, howler monkeys, and squirrel monkeys. They are known for their prehensile tails, which can be used as an additional limb for grasping.
Old World Monkeys: Old World Monkeys are found in Africa, Asia, and some parts of Europe. Examples include baboons, macaques, and langurs. They do not have prehensile tails and are more terrestrial compared to New World Monkeys.
Great Apes: The great apes include orangutans, gorillas, chimpanzees, bonobos, and homos (humans). Orangutans (genus Pongo): Orangutans are found in the rainforests of Borneo and Sumatra.
-Australopithecus: Australopithecus is a genus of early hominids that lived from around 4.2 to 2 million years ago. They had a more ape-like anatomy compared to later hominids, but they walked upright on two legs. Australopithecus species are considered to be among the ancestors of the Homo genus.
-Homo heidelbergensis: Homo heidelbergensis lived from approximately 700,000 to 200,000 years ago. They had larger brain sizes than earlier hominids and were likely the common ancestor of both Neanderthals and modern humans.
Neolithic Age (New Stone Age): The Neolithic Age began around 6,000 BCE and lasted until around 2,000 BCE in various regions. It is marked by the development of agriculture, animal domestication, and the emergence of permanent settlements. This period saw significant advancements in human civilization, including the invention of pottery and the transition from a nomadic to a more sedentary lifestyle.
Bronze Age: The Bronze Age started around 3,300 BCE and lasted until approximately 1,200 BCE, although the timeline varied in different regions. It is characterized by the widespread use of bronze, an alloy of copper and tin, for tools, weapons, and other artifacts. This era witnessed the rise of complex societies, the development of writing systems, and the emergence of early civilizations.
Iron Age: The Iron Age followed the Bronze Age and is marked by the advent and widespread use of iron tools and weapons. The exact starting and ending dates of the Iron Age vary depending on the region, but it generally began around 1,200 BCE and continued until the onset of historical periods and the rise of empires.
Ancient, Medieval, and Modern Eras: These eras represent broad periods in human history. The Ancient Era typically refers to civilizations and empires in the Mediterranean, Middle East, and Asia from the rise of city-states and early civilizations until the fall of the Western Roman Empire in 476 CE. The Medieval Era, also known as the Middle Ages, spans roughly from the 5th to the 15th century, characterized by feudal societies, the influence of the Catholic Church, and the rise of kingdoms and empires. The Modern Era encompasses the period from the Renaissance in the 14th century to the present day, marked by significant advancements in science, technology, exploration, colonization, and the development of democratic societies.
Key milestones in the Information Era include:
Personal Computers: The development and mass production of affordable personal computers in the 1970s and 1980s brought computing power to individuals and revolutionized the way people work, communicate, and access information.
Internet and World Wide Web: The invention of the internet in the late 1960s and the creation of the World Wide Web in the early 1990s provided a global network for sharing information and connecting people across the world. This led to an explosion of online services, e-commerce, social media, and other digital platforms.
Mobile Technology: The advent of mobile phones and smartphones, coupled with wireless communication technologies, further expanded access to information and connected people on the go. Mobile devices became powerful computing tools, integrating communication, internet access, and a wide range of applications.
Big Data and Analytics: The proliferation of digital data generated by individuals, organizations, and sensors led to the rise of big data analytics. This involves extracting insights and making informed decisions from large and complex datasets.
Internet of Things (IoT): The IoT refers to the network of interconnected physical devices, vehicles, appliances, and other objects embedded with sensors, software, and connectivity. It allows for the exchange of data and automation of various tasks, enhancing efficiency and convenience in daily life.
The Information Era has profoundly impacted various aspects of society, including communication, business, education, entertainment, healthcare, and more. It has transformed the way we access and share information, conduct research, collaborate, and interact with the world. The Information Era is an ongoing era that continues to evolve with the development of new technologies and the increasing integration of digital systems into our lives.
The process of evolution and natural selection generated the cells that form the organs that make us the organisms that we are. The main organs in the human body include the following:
Lungs: The lungs are respiratory sacks processing ambient air for the intake of oxygen and the disposal of carbon dioxide.
Liver: The liver is a multifunction organ performing over 500 bodily functions, including detoxification, nutrient metabolism, and storage of fat-soluble vitamins and minerals.
Kidneys: The kidneys are filters removing waste products from the blood via the production of urine. They also help maintain electrolyte balance, regulate blood pressure, and produce hormones.
Stomach: The stomach is the "washer" secreting enzymes and acids to break it down food and initiate the process of nutrient absorption.
Intestines: The small intestine continues the digestion and absorption of nutrients that began in the stomach. The large intestine finishes the digestive process, eliminating waste feces.
Pancreas: The pancreas produces digestive enzymes and regulates blood sugar levels in the body.
Skin: The skin is the largest organ of the human body, and serves as a protective barrier. It also regulates body temperature, and plays a role in sensation.
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