Zoology: Nature and Origin of Life

• National University (NU) Lipa offers Zoology programs, focusing on the nature of life and education that works.
• Zoology studies the nature of life.
• The study of Zoology enables the ability to:
• Relate the characteristics of life to the branches, theories, and principles of Biology
• Describe living things by citing characteristics distinct from inanimate objects
• Discuss theories explaining the origin of life comparatively

The Nature of Life

• Definition and Origin of Life includes properties and reproduction of life.
• Processes and Characteristics of Life includes types of metamorphosis, growth, metabolism, and evolution.
• Levels of organization are critical in understanding the nature of life.
• Theories on the Origin of Life are explored in Zoology.

Abiogenesis vs. Biogenesis

• Abiogenesis is the scientific theory that life arose on Earth spontaneously from non-living matter under conditions present at the time.
• The concept of abiogenesis is also known as "Spontaneous Generation".
• For a long time, people believed that flies came from rotten meat.
• Biogenesis refers to the concept that all living things come from other living things.
• Biogenesis gave rise to the cell theory and theories on the origin of life "LIFE came from LIFE."

Reproduction

• Reproduction in living organisms is either asexual or sexual.
• Asexual reproduction involves one parent, is very quick, produces many offspring, and results in low genetic variation; it involves mitosis.
• Sexual reproduction involves two parents, takes more time and energy, produces few offspring, and results in high genetic variation; it involves meiosis.
• Asexual reproduction types in animals include budding in hydra, parthenogenesis, fragmentation, and binary fission.

Reproduction Isolation Mechanisms

• Prezygotic isolating mechanisms include geographic, ecological, behavioral, temporal, and mechanical isolation and prevention of gamete fusion.

Geographic Isolation

• Geographic isolation is an example of adaptive radiation in Galapagos finches.

Ecological Isolation

• Ecological or habitat isolation is exemplified by different snake species occupying different habitats.

Behavioral Isolation

• Behavioral Isolation refers to the mating and courtship rituals.

Temporal Isolation

• Temporal isolation is species that breed during different times of day/year cannot interbreed.

Mechanical Isolation

• Mechanincal isolation is when left- vs. right-handed snail species can't mate

Gametic Isolation

• Gametic isolation is when sperm and egg of different sea urchin species are incompatible.

Postzygotic Isolation Mechanisms

• Postzygotic isolating mechanisms includes Hybrid inviability, Hybrid infertility, and Hybrid Breakdown

Postzygotic Isolation: Reduced Hybrid Viability

• Reduced hybrid viability: embryo doesn't live, such as with salamander hybrids that are frail or fail to mature.

Postzygotic Isolation: Reduced Hybrid Fertility

• Reduced hybrid fertility: hybrids develop but are sterile; for example, a horse and donkey produce a mule which is sterile.

Postzygotic Isolation: Hybrid Breakdown

• Hybrid (F2) breakdown means the F1 generation is fertile, but future generations are sterile or have reduced fitness, sometimes resulting in small hybrid rice plants.

Metamorphosis

• Development occurs as all organisms pass through a characteristic life cycle.
• Development involves the changes an organism undergoes from its origin to its final adult form.
• Three types of metamorphosis in insects include:
• Ametabolous with no metamorphosis, as seen in silverfish
• Hemimetabolous with incomplete metamorphosis where the nymph resembles the adult and there is no pupal stage; examples include plant bugs, crickets, true bugs, termites, grasshoppers, and cockroaches
• Holometabolous with complete metamorphosis, where larvae and adults are very different and a distinct pupae is formed; examples include beetles, flies, bees, lacewings, butterflies, ants, and caddis flies

Growth

• Two ways growth is achieved are:
• Accretion
• Intussusception
• Plants exhibit indeterminate/unlimited growth, while animals show determinate/limited growth.

Environmental interaction

• All animals interact with their environments.
• Ecology studies the interaction of organisms with an environment.
• Irritability, also known as the ability to be irritated, is the capacity of all organisms to respond to environmental stimuli.

Metabolism

• Metabolic process include:
• Digestion
• Energy production (respiration)
• Synthesis of required molecules and structures by organisms
• Organisms maintain themselves by acquiring nutrients from their environments.
• Metabolism involves both destructive catabolic and constructive anabolic reactions.
• Anabolic and catabolic chemical processes used by living systems arose early in the evolutionary history of life

Evolution

• It is the change in living things through time.
• Explains inherited similarities and the diversity of life.

Levels of Organization

• Living systems demonstrate complex hierarchical organization.
• The hierarchy of levels includes: macromolecules, cells, tissues, organs, organ systems, organism, population, community, and ecosystem.

Theories on the Origin of Life

• Abiogenesis suggests that life emerges from non-living matter and requires a vital force.
• Biogenesis suggests that life only arises from existing life.
• Francesco Redi experimented on Abiogenesis vs Biogenesis
• John Needham experimented on Abiogenesis vs Biogenesis
• Lazzaro Spallanzani experimented on Abiogenesis vs Biogenesis
• Franz Schulze experimented on Abiogenesis vs Biogenesis
• Theodor Schwann experimented on Abiogenesis vs Biogenesis
• Georg Friedrich Schröder & Theodor von Dusch in 1850 filtered air through sterile cotton wool, demonstrating no microbial growth.
• Felix Pouchet in 1859 claimed that microbial growth could occur without contamination.
• Louis Pasteur (1822-1895) disproved the doctrine of spontaneous generation.
• John Tyndall (1820-1893) demonstrated that dust carries microorganisms and provided evidence of exceptionally heat-resistant forms of bacteria, known as Tyndallization.