12.3 Survey of Major Groups of Organisms

Life's diversity is mind-blowing. From tiny viruses to massive whales, organisms come in all shapes and sizes. This topic dives into the major groups, exploring their unique features and roles in ecosystems.

We'll check out microorganisms like bacteria and protists, then move on to fungi, plants, and animals. Each group has its own special traits that help it thrive in different environments.

Microorganisms

Viruses and Bacteria

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• Viruses are non-living infectious agents that require a host cell to reproduce
  • Consist of genetic material (DNA or RNA) surrounded by a protein coat
  • Can infect all types of organisms (bacteria, plants, animals)
• Bacteria are prokaryotic microorganisms that lack a nucleus and other membrane-bound organelles
  • Vary in shape (spherical, rod-shaped, spiral) and can be found in diverse environments (soil, water, human gut)
  • Some bacteria are beneficial (aid in digestion, produce antibiotics) while others can cause diseases (strep throat, pneumonia)

Archaea and Protists

• Archaea are single-celled organisms that lack a nucleus and are similar to bacteria in structure
  • Thrive in extreme environments (hot springs, salt lakes, deep-sea vents)
  • Play important roles in nutrient cycling and can produce methane gas
• Protists are diverse eukaryotic organisms that are not plants, animals, or fungi
  • Include algae (kelp, diatoms), protozoa (amoebae, paramecia), and slime molds
  • Can be unicellular or multicellular and exhibit a wide range of behaviors (photosynthesis, predation, parasitism)

Eukaryotic Kingdoms

Fungi

• Fungi are eukaryotic organisms that absorb nutrients from their surroundings
  • Include mushrooms, yeasts, and molds
  • Play crucial roles as decomposers, breaking down dead organic matter and recycling nutrients
  • Form symbiotic relationships with other organisms (lichens, mycorrhizae)
• Fungi have cell walls made of chitin and reproduce through spores
  • Some fungi are used in food production (bread, beer, cheese) and medicine (antibiotics)

Plants

• Plants are multicellular eukaryotic organisms that obtain energy through photosynthesis
  • Contain chloroplasts, cell organelles that convert sunlight into chemical energy
  • Have cell walls made of cellulose and are usually terrestrial
• Plants exhibit a wide range of diversity, from small mosses to giant sequoias
  • Are classified into non-vascular (mosses, liverworts) and vascular plants (ferns, gymnosperms, angiosperms)
  • Provide oxygen, food, and habitat for many other organisms

Animals

• Animals are multicellular eukaryotic organisms that are heterotrophs (obtain energy by consuming other organisms)
  • Lack cell walls and are usually motile at some stage of their life cycle
  • Exhibit a wide range of body plans, from simple sponges to complex vertebrates
• Animals play important roles in ecosystems as consumers, predators, and prey
  • Are classified into vertebrates (animals with backbones) and invertebrates (animals without backbones)

Animal Diversity

Vertebrates

• Vertebrates are animals with a backbone and an internal skeleton
  • Include fish, amphibians, reptiles, birds, and mammals
  • Have a well-developed nervous system, a closed circulatory system, and specialized organs for respiration and excretion
• Vertebrates have evolved a wide range of adaptations for living in diverse environments (fins for swimming, wings for flying, fur for insulation)
  • Some vertebrates are ectothermic (cold-blooded) while others are endothermic (warm-blooded)

Invertebrates

• Invertebrates are animals that lack a backbone and an internal skeleton
  • Include sponges, cnidarians (jellyfish, corals), flatworms, roundworms, mollusks (snails, octopuses), annelids (earthworms, leeches), arthropods (insects, spiders, crustaceans), and echinoderms (sea stars, sea urchins)
  • Make up the majority of animal species and are found in nearly every habitat on Earth
• Invertebrates exhibit a wide range of body plans and adaptations
  • Some have hard exoskeletons (arthropods) while others have soft bodies (mollusks)
  • Many invertebrates have complex life cycles with multiple stages (larvae, pupae, adults)

Biodiversity

• Biodiversity refers to the variety of life on Earth at all levels, from genes to ecosystems
  • Includes the diversity of species, the genetic variation within species, and the diversity of ecosystems
  • Is essential for the stability and resilience of ecosystems and the provision of ecosystem services (pollination, nutrient cycling, climate regulation)
• Biodiversity is threatened by human activities such as habitat destruction, overexploitation, pollution, and climate change
  • The current rate of species extinction is estimated to be 100 to 1000 times higher than the natural background rate
  • Efforts to conserve biodiversity include protected areas, species recovery plans, and international agreements (Convention on Biological Diversity)