Ecology Lecture Notes Flashcards

Population Dynamics

• Population size change over time is influenced by:
  • Per capita birth rate (b): births per individual.
  • Per capita death rate (d): deaths per individual.
  • Per capita rate of increase (r): r = b - d

Scenarios based on r:

• If r > 0, population increases.

• If r < 0, population decreases.

• If r = 0, zero population growth, constant population size.

  • Example: If b = 0.4 and d = 0.4, then r = 0

Logistic Growth Model

• S-shaped curve: Population size increases over time but levels off at carrying capacity (K).

• Equation: \frac{dN}{dt} = r_{\text{max}} N \frac{(K - N)}{K} where:

  • N = Population size
  • K = Carrying capacity

• Impact of N on growth rate:

  • Small N: Fast growth, steep slope.
  • Large N (close to K): Slow growth, resources limited.

Species Interactions

• Competition: Negative impact for one or both species.
• Neutral impact.

Niche Concept

• Niche: Combination of abiotic and biotic factors used by an organism.

Niche Factors

• Single-factor niche.
• Two-factor niche (e.g., temperature).
• Three-factor niche (e.g., salinity, temperature).

Types of Niches

• Fundamental niche: Physiological niche under ideal conditions.

  *Ideally, where a species could be found.

• Realized niche: Actual niche where a species is found.

  • Realized niche is smaller than the fundamental niche.

Competition

• Competition: Two species require the same resource in limited supply.

• In nature: Results in competition or avoidance of competition.

• Experimental evidence: Lab-based study on two different species of paramecium demonstrates logistic growth under limited resources.

• Competitive Exclusion Principle: Trade-off between tolerating drying out and competitive ability.

  • Example: Barnacles (Balanus and Chthamalus).
  • Chthamalus from that lower region competitive ability

Avoiding Competition

• Strategies:

  • Evolve to use a different resource.

  • Occupy different niches.

  • Example: Anolis lizards occupying different microhabitats.

• Competitive exclusion does not always lead to extinction.

• Example: Invasive Argentine ant species compete with native ant species.

Competitive Exclusion Principle

• Niche overlap: Species competing for the same resources.

• Evolutionary adaptation: Occupy different niches to coexist or go extinct.

• Character Displacement: Trait differs between two species when found in sympatry (same geographic region).

  • Sympatry vs. allopatry: Species inhabiting the same geographic region at the same time vs. species isolated by an external barrier.

  • Trait differing is directly related to competition.

  • Example: Beak depth in finches on islands.

    • When multiple species on 1 island, this is what we don't see when compared to different islands.

    • Beak depth influenced by competition.

Keystone Species

• Highly influential to their ecosystem; removal can dramatically decrease diversity.

  • Example: Yellowstone wolves.

Predator-Mediated Coexistence

• Keystone predator (e.g., seastar) allows two species to coexist by:

  • Selective predation favoring coexistence.

  • Example: Barnacles and mussels.

    • Without seastar: Mussels competitively exclude barnacles.
    • With seastar: Predation prevents mussels from taking over, promoting coexistence.

  • Higher species diversity when the predator is present, preventing competitive exclusion.

Ecological Succession

• Predictable change in community over time, associated with disturbance.

Types of Succession

• Primary succession: Occurs in a "lifeless" area with no soil due to disturbance.
• Secondary succession: An earlier community is disturbed and returns to an earlier stage in the successional sequence.

Life-History Trade-offs

• Species present are characterized by trade-offs in their life-history:
  • r-selected traits: Species that show up early, smaller size, colonize quickly; not very competitive (e.g., weeds).
  • K-selected traits: Species that show up later, larger size, colonize slower, grow slowly; very competitive (e.g., larger seeds, red woods, oaks, maples).

Ecological Succession and Diversity

• Early and late stages: Lowest species diversity.
• Intermediate stages: Highest species diversity.

Whale Carcass Example

• Complex "mini" ecosystem.

  • Early stages: Low species diversity.
  • Intermediate stages: 178 species on a single vertebra.

Ecosystem Energy Flow

• Energy flows through ecosystems.

Autotrophs

• At the base of the energy: Autotrophs (e.g., plants, green algae, cyanobacteria) produce energy through photosynthesis.

Trophic Structure

• Describes the feeding relationships of organisms.

• Producers (Autotrophs):

  • Terrestrial systems: Plants.
  • Aquatic systems: Phytoplankton.
  • Deep ocean: Chemosynthetic prokaryotes (energy from chemicals).

• Consumers:

  • Herbivores: Eat producers.

  • Carnivores: Eat other consumers.

  • Omnivores: Eat producers and consumers.

  • Detritivores/Decomposers: Feed on dead/decaying matter (detritus).

    • Examples: millipedes, sea cucumbers.

  • Decomposers: Feed on dead plant/animal matter (fungi, bacteria, earthworms).

  • Scavengers: Eat dead animals (Vultures).

Food Chain

• Linear sequence of feeding relationships describing energy transfer.

Food Web

• Network of food chains; more realistic.

Trophic Levels

• Primary consumers.

• Secondary consumers.

  • Example: Crabeater seals (2° consumers).

Energy Transfer and Energy Pyramids

• Energy is lost between trophic levels due to:

  • Respiration.
  • Waste.

• The rest of the energy makes the transition used in secondary production growth of an individual.

• 90% reduction in energy at each trophic level

  • Energy Pyramids
    • If producers (phytoplankton) have 100,000 J, then the Primary consumer (zooplankton) has 10,000 J, the Secondary consumer has 1000 J, the tertiary consumer has 100 J, and the Quaternary consumer has 10 J

Chemical Cycling

• Chemical elements are available only in a limited amount and must be recycled.
• Biogeochemical cycles: Nutrient cycles with living (biotic) and non-living (abiotic) components.

Reservoirs

• Overall reservoirs:
  • Organic (O): Living material (must contain carbon).
  • Inorganic (I): Non-living components (soil, atmosphere).
• Availability:
  • Available (A): Accessed directly (e.g., eating, uptake from water/air).
  • Unavailable (V): Not accessed directly (e.g., rock, minerals).

Carbon Cycle

• Important because it forms the framework for all organic molecules.
• CO_2 is used in photosynthesis by plants (1° producer) and the carbon is available for consumers.
  • Grasshoppers eat Plants (1° consume) -> Mouse (2° consumer) eats grasshopper

Nitrogen Cycle

• Importance:

  • Part of amino acids, proteins, nucleic acids.
  • Often a limiting plant nutrient.

• 80% of N_2 is in the atmosphere, but plants can't access it.

• Nitrogen-fixation done by bacteria (prokaryotes): Convert N2 to ammonia (NH3) + ammonia.

• Plants use inorganic forms of nitrogen: NH4, NO3

Phosphorus Cycle

• P is part of ATP, nucleic acids, RNA, and DNA.
• Plants use inorganic form (phosphate; PO_4).
• Largest reservoir: Sedimentary rock (phosphate minerals).

Diversity of living Organisms

• Unity of life – Similarities in organisms

  • all have same 20 a.a ATP
  • DNA as genetic material
  • homologies in bone structure

• Diversity of Life - Many different species that exist, is driven by evolution + natural Selections

  • Causing new traits

• Some Sort of metabolism (to process energy)

• reproduce. - asexual VS Sexval

• Organized structure - cells have a different Structure

• movement I response to enviroment - plants change

• grow develop - in response to enviroment change

• evolutionary adaptation - to Survive

• Regulate internal enviroment - homostasis.

Prokaryotes

• Most abundant life form on Earth.

  • Most are bacteria - Rhizobia, Bacillus sp.
  • Also Archaea - thermophiles, halophiles, methanogens

• Small (0.5-5 mm in length).

• Single-celled - no nucleus (no membrane bound organelles).

• Asexual reproduction- binary fission (one bacterial cells divides its DNA in half)

• Undergo rapid evolution because of their quick reproduction.

• Use flagella for movement (not all but some).

• pathogenic bacteries

Archaea or Bacteria?

• Cell Walls:

  • Bacteria: have peptidoglycan in their cell wall (rigid envelope for protection)
  • Archaea: no peptidoglycan in cell wall

• Growth at temperature > 100°C in cell wall

  • Bacteria: no
  • Archaea: yes for some species (extremophiles)

• Variation in Bacteria and Archaea

  • mutation because no sexval reproduction -> Change in DNA sequence
  • Horizontal transfer some genetic material -> exchanging of sance spp.

Prokaryotes - Source of Carbon

• • Heterotrophs: get Some Organic compound from their source from Sume other organism
  • Autotrophs: absorb + take in things from exviroment for example, Sunlight to Sulfur)

Prokaryotes Ecology

• Critical role in chemical cycling:

  • Nitrogen cycle (by fixing N_2 = make it available to plants).
  • Carbon cycle through decomposition & photosynthesis.

Protists

• Eukaryotes meaning they have membrane-bound organelles.
• Typically unicellular with a complex organization within their cells.
• Cell wall made of cellulose.
• Phylogenetic Velationships are often unclear because of this huge complexity within protists.
• Varied modes of reproduction -> is binary fission -> asexually- mitosis / Sexually-meiosis

What are fungi?

• heterotrophs - get nutrients from outside themselves
• Cells Walls have Chitin.
• Asexual / Sexual reproduction produce many spores. - Type III
  • Spores - produced by reproductive structure
    1. Wind disposual
    2. Water droplets disposual
    3. Attract insects - through scent
  • asexually- Stoday honeydew substance
• have diverse Roles
  • Mutulists
    • Lichen - relationship between fungus, bacteria, photosynthetic protist
• - Lichen is vary important Panar Species on Ground when species are not many
  - often found on rocks / trees. role in Succession
• Mutualist + (mycorrhizae) fungi and plant roots fungi and plant roots.
  - fungi help root absorption + give nutrient / Plant give Carbohydrates fungi through Photosynthesis