Lecture 15: Fungi

Fungal Phylogeny and Characteristics

Fungi are a diverse kingdom of eukaryotic organisms that play essential roles in ecosystems as decomposers, symbionts, and pathogens. Understanding their placement in the tree of life and their unique features is fundamental in biology.

• Phylogenetic Placement: Fungi are more closely related to animals than to plants, sharing a common ancestor with animals in the Opisthokonta supergroup.

• Synapomorphies: Key shared traits include chitin in cell walls, absorptive heterotrophy, and the production of spores.

• Fungal Morphology: Fungi exhibit structures such as hyphae (filamentous cells) and mycelium (networks of hyphae). Specialized structures include mycorrhizae (symbiotic associations with plant roots), spores (reproductive units), and fruiting bodies (e.g., mushrooms).

• Generalized Fungal Life Cycle: Most fungi have a life cycle that includes both sexual and asexual reproduction, often involving haploid, dikaryotic, and diploid stages.

• Fungal Movement: Fungi do not move via flagella (except some chytrids); instead, they grow by extending hyphae.

Example: Mycorrhizal fungi form mutualistic relationships with plant roots, enhancing nutrient uptake for plants and receiving carbohydrates in return.

Lectures 16-17: Animal Diversity

Animal Synapomorphies and Body Plans

Animals are a monophyletic group characterized by unique features and diverse body plans. Understanding these traits and evolutionary milestones is key to studying animal diversity.

• Shared Traits: Animals are multicellular, heterotrophic, lack cell walls, and have specialized tissues (except sponges).

• Animal Body Plans: Body plans differ in symmetry (radial vs. bilateral), number of tissue layers (diploblastic vs. triploblastic), and presence of a coelom (body cavity).

• Major Animal Clades: Key clades include Porifera (sponges), Cnidaria (jellyfish, corals), Protostomes (arthropods, mollusks), and Deuterostomes (echinoderms, chordates).

• Cambrian Explosion: A period (~541 million years ago) marked by rapid diversification of animal body plans and the appearance of most major animal phyla.

• Vertebrate Evolution: Major milestones include the development of jaws, limbs, amniotic eggs, and adaptations for terrestrial life.

Example: The transition from aquatic to terrestrial environments in vertebrates required adaptations such as lungs and limbs.

Lectures 18-19: Behavioral Ecology

Animal Behavior and Evolution

Behavioral ecology examines how animal behavior is shaped by ecological and evolutionary pressures. It includes the study of learning, mating systems, and foraging strategies.

• Proximate vs. Ultimate Causes: Proximate causes explain how behaviors occur (mechanisms), while ultimate causes explain why behaviors evolved (adaptive value).

• Innate vs. Learned Behaviors: Innate behaviors are genetically programmed; learned behaviors are acquired through experience.

• Types of Learning: Includes habituation, imprinting, associative learning, and social learning.

• Mating Systems: Types include monogamy, polygyny, and polyandry, each with different implications for sexual selection and parental investment.

• Sexual Selection: Selection for traits that increase mating success, often leading to sexual dimorphism.

• Optimal Foraging Theory: Predicts that animals will maximize energy gained per unit time spent foraging.

Example: Male peacocks display elaborate tails to attract females, a classic case of sexual selection.

Lecture 20: Intro to Ecology

Levels of Organization and Ecological Patterns

Ecology is the study of interactions among organisms and their environment, organized into hierarchical levels.

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

• Ecological Patterns and Processes: Patterns include species distributions and abundance; processes include energy flow and nutrient cycling.

• Scales: Ecological phenomena occur at spatial (local to global) and temporal (short to long-term) scales.

• Abiotic and Biotic Factors: Abiotic (non-living) factors include climate and soil; biotic (living) factors include interactions among organisms.

• Climographs: Graphs that plot temperature and precipitation to predict biome types.

Example: A climograph can help determine whether a region is a tropical rainforest or a desert based on its climate data.

Lectures 21-22: Population Ecology

Population Dynamics and Growth Models

Population ecology focuses on the factors that affect population size, growth, and structure over time.

• Population vs. Species: A population is a group of individuals of the same species in a given area.

• Population Growth Models: Includes exponential and logistic growth models.

• Exponential Growth Equation:

• Logistic Growth Equation:

• Life History Strategies: r-selected species produce many offspring with low survival; K-selected species produce fewer offspring with higher survival.

• Survivorship Curves: Type I (high survival early), Type II (constant mortality), Type III (high mortality early).

• Density-Dependent vs. Density-Independent Factors: Density-dependent factors (e.g., competition, disease) intensify as population increases; density-independent factors (e.g., weather) affect populations regardless of size.

Example: Human populations often exhibit Type I survivorship curves, while many fish exhibit Type III.

Lecture 23-24: Community Ecology

Species Interactions and Community Structure

Community ecology studies the interactions among species and how these shape community composition and dynamics.

• Species Interactions: Includes competition, predation, herbivory, parasitism, mutualism, commensalism, and amensalism.

• Fundamental vs. Realized Niche: The fundamental niche is the full range of conditions a species can occupy; the realized niche is where it actually exists due to biotic interactions.

• Food Webs: Diagrams showing feeding relationships among species in a community.

• Succession: The process of change in species composition over time, including primary (on new substrates) and secondary (after disturbance) succession.

• Species Richness and Diversity: Influenced by factors such as disturbance, area, and proximity to other communities.

Example: After a forest fire, secondary succession leads to the gradual return of plant and animal species.

Lecture 25-27: Ecosystems Ecology to End

Cycles of Matter, Productivity, and Biodiversity

Ecosystem ecology examines energy flow and nutrient cycling, as well as the importance of biodiversity and the impacts of human activity.

• Cycles of Matter: The water, carbon, nitrogen, and phosphorus cycles move essential elements through ecosystems.

• Net Primary Productivity (NPP): The rate at which plants convert solar energy into biomass, minus the energy used in respiration.

• Biodiversity: The variety of life at genetic, species, and ecosystem levels; essential for ecosystem resilience and function.

• Major Threats to Biodiversity: Habitat destruction, invasive species, overexploitation, and climate change.

• Mitigation: Conservation efforts, habitat restoration, sustainable resource use, and policy changes can help protect biodiversity.

Example: Tropical rainforests have high NPP and biodiversity but are threatened by deforestation.

Table: Comparison of r-Selected and K-Selected Species