Biological Concepts in Ecology and Botany

Origins of Life

• Phylogeny is the evolutionary tree
• Biodiversity is the diversity of life, including genetic, taxonomic, and ecosystem diversity
• Morphology refers to the shape of a species

What is a Species? And How Many?

• It is difficult to precisely define a species
• Biological Species Concept: a group of populations that can interbreed and are reproductively isolated from other such populations
• Problems with BSC:
  • It's often hard to observe reproductive isolation in species
  • Some clearly distinct species can interbreed (e.g., a liger)
  • It does not apply to fossil species
  • Defining species in prokaryotes (Archaea and Bacteria) is difficult because of DNA exchange
  • Species are classified based on DNA similarity; 97% similarity indicates the same species
• Eukaryotes: organisms with complex cells (plants, animals, and fungi)
  • Estimates of eukaryotic species:
    • 8.7 million
    • 5-3 million

How Can We Assess Diversity?

• Taxonomy is the identification, description, naming, and classification of organisms
• Systematics/classification: the organization of organisms into groups according to some system
• Phylogenetics: a branch of biology studying evolutionary relationships
• Carl Linnaeus (1707-1778): Father of modern taxonomy
  • First to classify organisms
  • Introduced binomial nomenclature (genus and species names) for classifying organisms
  • Proposed classification ranks (kingdom, phylum, class, etc.)

An additional Rank

• An additional rank above Kingdom is Domain

Phylogenetics

• The study of evolutionary relationships between organisms
• Evolution outcomes:
  • Better adaptation to the environment
  • Speciation (formation of new species)
  • Extinction
• The tree of life is fundamental to Linnaean classification

Eukaryotes

• Earliest eukaryotes: 1.65 billion years ago
• Earliest multicellular eukaryotes: 1.635 billion years ago
• Eukaryotes are diverse and have complex cells and life cycles
• Eukaryotes have evolved multicellularity
  • Many have distinctive features like a nucleus within their cells
  • Larger genomes than prokaryotes
• Eukaryotes sometimes reproduce sexually to promote genetic variation
  • Processes include meiosis (haploid cells from diploid cells) and fertilization (diploid cells formed from two haploid cells)
  • All cells are either haploid or diploid

Cells

• Nuclei separate processes like DNA replication and transcription from translation which provides additional gene expression regulation
  • DNA is structured into linear chromosomes within the nucleus
• Mitochondria: Present in most eukaryotes (sometimes lost). Essential for cellular respiration
  • Some eukaryotes lose mitochondria due to parasitic nature
  • Mitochondria are considered to have arisen from free-living bacteria that evolved into eukaryotes
• Chloroplasts: Photosynthetic organelles in plants and algae
  • Originate from free-living bacteria
• Cells compartmentalized into specialized components.

Diversity of Eukaryotes

• Most eukaryotes are single-celled organisms called protists
• Protists can be related to animals, plants, or fungi
• Some protists known as excavates are important parasites (Giardia and Trichomonas)
  • Lack/reduced mitochondria

Alveolates

• A type of protist that includes dinoflagellates, important marine plankton that are photosynthetic and can produce red tides that harm wildlife and produce bioluminescence
  • Also includes important parasites (e.g. Trichomonas)

Slime Moulds

• Usually single-celled organisms, but they can form a multicellular body when food is scarce.

Algae

• Most algae are photosynthetic
• Algae have varying levels of complexity from unicellular to multicellular forms.
  • Green algae are related to land plants
  • Red algae include some edible seaweed
  • Brown algae include seaweeds like kelp which are large multicellular organisms that can form forests in the ocean

Plants (Embryophyta)

• Plants are multicellular
• Majority are terrestrial and obtain energy from photosynthesis
• Plants have complex reproductive cycles, alternating between haploid and diploid stages
• Sporophytes are the diploid stage (producing spores)
  • Gametophytes are the haploid stage (producing gametes)
• Land plants evolved from a group of green algae
• The oldest known land plants evolved about 430 million years ago and were mostly small

Adaptation

• Plants on land had challenges like maintaining moisture
• Plants' developed cuticles and stomata (pores) to address this

Non-vascular Plants

• Lack vascular tissue, which are critical for transporting water and nutrients

Vascular Plants

• Have xylem (water transport) and phloem (nutrient transport)

Seeds and Flowers

• Seeds and flowers are a characteristic of many plants
• The ability to reproduce through seeds is a key adaptation leading to diverse plant groups
• Different plant groups:
  • Ferns
  • Gymnosperms (conifers, cycads)
  • Angiosperms (flowering plants)
• Angiosperms are critical to human activities

Earth's Biomes

• Earth's biomes are largely determined by plant communities
• Examples include tundra, grasslands, forests

Opisthokonts

• Animals and Fungi are closely related; both are eukaryotes and include a number of important parasites
• They are all Opisthokonts
• Have single posterior flagella

Fungi

• Fungi are heterotrophs, obtaining nutrients by secreting digestive enzymes and absorbing dissolved molecules
• Fungi are a critical part of many ecosystems; they decompose organic matter
• Many fungi are important to humans (food, antibiotics)

Animalia (Metazoa)

• Animals are motile (capable of active movement at some point in their life cycle)
• Animals are closely related to choanoflagellates (eukaryotes)
• Several phylum exist including:
  • Porifera (sponges): Simplest animals
  • Radiata (jellyfish, corals, sea anemones): Radial symmetry
  • Bilateria (most animals): Bilateral symmetry

Sponges

• Simplest animals (no true tissues)
• Feed by filtering water into their bodies
• Have specialized cells to move water and capture food particles

Cnidarians (jellyfish, corals)

• Contain specialized stinging cells called nematocysts
• Can exist as polyps (sessile) or medusae (free-swimming)
• Corals are colonial organisms that build up coral reefs

Bilateria

• Majority of animals
• Some are bilaterally symmetrical
• Triploblastic (3 germ cell layers)
• Often have a body cavity (coelom)

Protostomes

• A major lineage of bilaterian animals
• Two major groupings:
  • Lophotrochozoa
  • Ecdysozoa

Lophotrochozoa

• Includes organisms with feeding structures called lophophores and larvae called trochophores
  • Examples include molluscs (snails, clams), annelids (worms)

Ecdysozoa

• Includes animals that shed their external covering (cuticle) during growth
• Many groups within like arthropods and nematodes

Arthropods

• Have external skeletons, segmented bodies, and jointed appendages
• Includes insects, crustaceans, spiders.

Mollusk

• Diverse group of animals (snails, clams, squid)
• Often have a shell and a muscular foot
• Many have a mantle that secretes the shell

Cephalopods (squid, octopus)

• Some of the most intelligent invertebrates
• Use complex behaviors and sophisticated sensory systems.

Annelids

• Segmented worms (earthworms, leeches)
• Have repetitive segments

Nematodes

• Roundworms, parasitic in a wide range of organisms
• Important decomposers and in some ecosystems

Tardigrades

• Water bears, can survive extreme conditions

Onychophora

• Velvet worms

Crustaceans

• Aquatic arthropods (crabs, shrimp)
• Often have a hard exoskeleton

Hexapods

• Insects
• Usually have three pairs of legs

Malacostraca

• Diverse group of crustaceans.

Test your knowledge on species definitions and ecological roles within the Biological Species Concept, as well as the characteristics and classifications of plants and fungi. This quiz covers the challenges of applying the BSC to prokaryotes, types of algae, and the ecological significance of various organisms. Dive into questions regarding multicellular algae, nutrient acquisition in fungi, and plant adaptations.