Block 4 Biology: Plants, Fungi, Invertebrates, Vertebrates, Mammals, and Ecology

Origin and Cladogram of Plants

Origin of Plants

Modern plants evolved from green algae, a group of aquatic protists. The transition to land required adaptations for survival and reproduction outside water.

• Key Points:

  • Green algae are the closest relatives of plants, sharing similar chlorophylls and cell wall structures.

  • Plant adaptations include multicellularity, photosynthesis, and the development of spores.

  • Fossil record indicates land plants appeared over 470 million years ago.

• Cladogram: Shows evolutionary relationships among major plant groups, from non-vascular to vascular and seed plants.

Additional info: Plants evolved mechanisms to survive independently from water, such as cuticles and stomata.

Plants' Adaptations to Survive and Reproduce on Dry Land

Key Adaptations

Plants developed several adaptations to thrive on land, including desiccation resistance and specialized reproductive strategies.

• Alternation of Generations: Life cycle alternates between multicellular haploid (gametophyte) and diploid (sporophyte) stages.

• Walled Spores: Spores are coated with sporopollenin, a tough polymer that prevents dehydration and aids dispersal.

• Apical Meristems: Regions at the tips of roots and shoots where cells divide for growth, allowing plants to access nutrients and sunlight.

• Cuticle: Waxy layer on the epidermis that prevents water loss.

• Stomata: Pores that regulate gas exchange and water loss.

Together, these adaptations allow plants to survive independently of aquatic environments.

Main Features and Ecological Importance of Non-Vascular Plants

Non-Vascular Plants (Bryophytes)

Bryophytes include mosses, liverworts, and hornworts. They are small, non-woody plants lacking vascular tissue.

• Key Features:

  • Dominant gametophyte stage in life cycle.

  • Simple structure: No true roots, stems, or leaves.

  • Require water for fertilization: Sperm must swim to egg.

  • Asexual reproduction: Fragmentation or gemmae.

• Ecological Importance:

  • Nitrogen cycling: Mosses can harbor nitrogen-fixing cyanobacteria.

  • UV protection: Produce compounds that absorb harmful radiation.

  • Soil stability: Bryophytes form mats that prevent erosion and retain water.

  • Bioindicators: Sensitive to acid rain and pollution.

Main Features and Ecological Importance of Seedless Vascular Plants

Seedless Vascular Plants

Includes ferns and lycophytes, the first plants to evolve vascular tissues (xylem and phloem).

• Evolutionary Background: Appeared about 425 million years ago, allowing greater size and complexity.

• Major Features:

  • Vascular tissues: Xylem (water transport) and phloem (nutrient transport).

  • Dominant sporophyte stage: Larger and more complex than gametophyte.

  • Roots, stems, leaves: Specialized organs for support and nutrient absorption.

  • Spore production: Spores produced in sporangia; heterospory in some groups.

• Ecological Importance:

  • Transformed Earth's ecosystems, producing the first forests.

  • Ancient seedless vascular plants contributed to the formation of coal deposits.

  • Increased oxygen levels and shaped early terrestrial food webs.

Feature	Non-Vascular (Bryophytes)	Seedless Vascular (Ferns & Lycophytes)
Dominant Generation	Gametophyte	Sporophyte
Vascular Tissue	Absent	Present (xylem & phloem)
Water Requirement	Required for fertilization	Still needed, but less dependent
Reproduction	Spores	Spores

Vascular Plants with Seeds & Fungi

Distinctive Features of Vascular Plants with Seeds (Seed Plants)

Seed plants include gymnosperms and angiosperms. They have several key adaptations for reproduction and survival.

• Reduced Gametophytes: Seed plant gametophytes are microscopic and develop inside the sporophyte.

• Heterospory: Production of two types of spores: megaspores (female) and microspores (male).

• Ovules: Structure containing the female gametophyte and integuments; after fertilization, develops into a seed.

• Pollen: Male gametophyte; allows fertilization without water.

• Evolutionary Advantages of Seeds:

  • Protection from desiccation and predators

  • Long dormancy and dispersal

  • Food supply for embryo

  • Long-distance dispersal (wind, animals, water)

Divisions of Vascular Plants with Seeds

• Gymnosperms: "Naked seeds" not enclosed in fruit; examples: pines, firs, redwoods.

• Angiosperms: Seeds enclosed in fruits; flowers; make up 90% of plant species.

Importance of Seed Plants & Threats to Diversity

• Importance: Major food crops, wood, paper, medicines.

• Threats: Deforestation, habitat loss, climate change.

Fungi — Characteristics, Nutrition, Structure

• General Characteristics: Eukaryotic, found in all environments, heterotrophic, absorb nutrients, secrete hydrolytic enzymes.

• Nutritional Modes:

  • Decomposers: Break down dead organic matter.

  • Parasites: Feed on living hosts.

  • Mutualists: Form symbiotic relationships with plants.

• Body Structure: Hyphae (filaments), mycelium (network), septa (cross-walls), specialized hyphae for nutrition or mutualism.

• Reproduction: Sexual (plasmogamy, karyogamy, meiosis) and asexual (budding, spores).

Invertebrates

Characteristics of Kingdom Animalia

• Multicellular eukaryotes with collagen protein support.

• Heterotrophic: Ingest food.

• Nervous and muscle tissue (unique to animals).

Symmetry, Tissue Layers, & Body Cavities

• Symmetry: Radial (e.g., cnidarians) or bilateral (most animals).

• Germ Layers: Diploblastic (ectoderm, endoderm) or triploblastic (ectoderm, mesoderm, endoderm).

• Body Cavities: Coelomate (true coelom), pseudocoelomate, acoelomate.

Developmental Modes

• Protostomes: Mouth forms first.

• Deuterostomes: Anus forms first.

Major Invertebrate Phyla

• Porifera: Sponges; no true tissues, filter feeders.

• Cnidaria: Radial symmetry, gastrovascular cavity, polyp and medusa forms, cnidocytes for predation.

• Lophotrochozoans: Flatworms (planarians), mollusks (snails, clams, squids), annelids (segmented worms).

Invertebrates II & Vertebrates

Nematodes & Arthropods — Key Features

• Nematodes: Roundworms; found in diverse habitats, many are parasites, simple body plan.

• Arthropods: Segmented body, jointed appendages, exoskeleton, most successful animal phylum.

• Insects: Metamorphosis, specialized adults and larvae.

Vertebrates — General Characteristics

• Chordata: Bilateral symmetry, notochord, dorsal nerve cord, pharyngeal slits, post-anal tail.

• Notochord: Flexible rod supporting embryo; replaced by vertebral column in adults.

Major Vertebrate Lineages

• Jawless Fish: Hagfish, lampreys; no jaws, rudimentary vertebrae.

• Cartilaginous Fish: Sharks, rays; skeleton made of cartilage.

• Bony Fish: Ray-finned and lobe-finned fish; bony skeleton, swim bladder for buoyancy.

• Tetrapods: Four limbs, adapted for life on land.

• Amphibians: Frogs, salamanders; require moist habitats, eggs lack shells.

• Amniotes: Reptiles, birds, mammals; amniotic egg allows reproduction away from water.

Mammals & Human Evolution

Key Characteristics That Define Mammals

• Mammary glands: Produce milk for young.

• Hair (fur): Insulation, sensory input.

• Endothermy: Maintain stable internal body temperature.

• Powerful kidneys: Concentrate urine efficiently.

• Large brain: Complex behaviors and learning.

• Differentiated teeth: Specialized for various functions.

• Three middle ear bones: Unique to mammals, improve hearing.

Major Mammalian Groups: Monotremes, Marsupials, Placentals

• Monotremes: Egg-laying mammals (platypus, echidna); found only in Australia/New Guinea.

• Marsupials: Pouched mammals (kangaroo, koala); short gestation, young develop in pouch.

• Placentals (Eutherians): Most diverse group; long gestation, young develop internally.

Feature	Monotremes	Marsupials	Placentals
Reproduction	Lay eggs	Live birth	Live birth
Development	Outside body (egg)	Short pregnancy, long pouch	Long internal pregnancy
Nipples	No	Yes	Yes
Distribution	Australia & New Guinea	Australia & Americas	Worldwide

Mammalian Adaptations to Different Environments

• Marine adaptations: Insulation, buoyancy, energy storage.

• Flight in bats: Only mammals capable of true flight.

• Endothermy: Stable body temperature in diverse climates.

• Desert adaptations: Water conservation, nocturnal behavior.

• Cold climate adaptations: Thick fur, seasonal behaviors.

• Migration & hibernation: Seasonal movement and dormancy.

• Social systems: Complex group behaviors.

• Primate color vision: Trichromatic vision in primates.

Main Trends in Hominin Evolution

• Primates: Opposable thumbs, large brains, complex social groups.

• Humans and apes: Share a common ancestor; DNA similarity ~99%.

• Distinct human traits: Bipedalism, brain expansion, tool use, culture.

• Major hominin species: Homo habilis, Homo erectus, Homo neanderthalensis, Homo sapiens.

Ecology

Concept of Ecology

Ecology is the scientific study of interactions between organisms and their environment.

• Key Questions:

  • Where organisms occur

  • Why they occur there

  • How they interact

• Levels of Organization: Individual, population, community, ecosystem, biosphere.

Factors Affecting the Presence of Organisms

• Abiotic factors: Climate, temperature, rainfall, humidity, soil, nutrients, light.

• Biotic factors: Food, space, light, mates, competition, predation, mutualism.

Properties of a Population

• Density: Number of individuals per unit area.

• Age structure: Proportion of individuals in different age classes.

• Spatial distribution: Clumped, uniform, or random.

• Gene pool: All genes in a population.

Density Dependence vs Density Independence in Population Growth

• Exponential growth (density-independent): Occurs when resources are unlimited. $G = rN$

• Logistic growth (density-dependent): Occurs when resources are limited. $G = rN \left(\frac{K-N}{K}\right)$ Where $K$ is carrying capacity.

Concept of a Community

• A community is all the different species that live together in a particular area and interact.

• Community structure includes:

  • Species richness

  • Types and strengths of interactions

Interactions Between Species

• Neutralism: No effect on each other.

• Mutualism: Both benefit.

• Commensalism: One benefits, other unaffected.

• Amensalism: One harmed, other unaffected.

• Competition: Both harmed by shared resource use.

• Parasitism: One benefits, other harmed (not usually killed).

• Predation: One benefits by killing and eating the other.

Food Webs and Ecosystem Stability

• Food web: Network of feeding relationships; more complex than a simple food chain.

• Stability: Ability of an ecosystem to resist change when disturbed.

• Resilience: Ability to return to original state after disturbance.

Primary Productivity in Terrestrial vs Aquatic Ecosystems

• Primary productivity: Rate at which autotrophs convert inorganic carbon (CO2) into organic matter.

• Terrestrial ecosystems: Controlled by water, temperature, soil nutrients.

• Aquatic ecosystems: Controlled by nutrient availability (N, P, Fe, Si).

Population Growth Formula:

$P(t) = P_0 e^{rt}$

Where $P(t)$ is population at time $t$, $P_0$ is initial population, $r$ is growth rate.