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Biodiversity: Species Diversity and Distribution Patterns, Exams of Biology

University of Central Florida (UCF)Biology

Lecture notes on biodiversity, covering key concepts such as species diversity, speciation, species distribution, and the factors influencing biodiversity patterns. it explores different types of species diversity (alpha, beta, gamma), examines how species composition is determined at local, regional, and global scales, and discusses the roles of abiotic and biotic factors in shaping species ranges. the notes also delve into population dynamics, including population growth, control, and distribution patterns. finally, it touches upon the historical context of biogeography and continental drift in explaining species distributions. This detailed overview is valuable for students studying ecology and evolutionary biology.

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2024/2025

Available from 05/27/2025

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BIOL 1070 - Midterm # 2
Lecture Notes
Lecture 8:
What is biodiversity?
Possible answers:
• Number of species in a specific area
• Variability between species
• Number of species in a taxonomic group or clade
• Number of ecological roles filled by organisms in an area
• Variability within a species
Variation – Differences among individuals within a population.
Diversity – Number of species in an area/taxon/clade. Also called species richness.
Disparity – How different species are from each other.
What determines global biodiversity?
Global biodiversity is the net outcome of two opposing processes:
• Diversification through speciation.
• Loss of diversity through extinction.
How do new species form?
➢The formation of new species is called speciation.
➢Most often, this involves an ancestral species splitting or branching into two descendant
species. This is called cladogenesis.
What matters most for speciation is that there is a barrier to
gene flow, which allows one species to split into two.
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BIOL 1070 - Midterm # 2

Lecture Notes

Lecture 8:

What is biodiversity? Possible answers:

  • Number of species in a specific area
  • Variability between species
  • Number of species in a taxonomic group or clade
  • Number of ecological roles filled by organisms in an area
  • Variability within a species Variation – Differences among individuals within a population. Diversity – Number of species in an area/taxon/clade. Also called species richness. Disparity – How different species are from each other. What determines global biodiversity? Global biodiversity is the net outcome of two opposing processes: **- Diversification through speciation.
  • Loss of diversity through extinction. How do new species form?** ➢ The formation of new species is called speciation. ➢ Most often, this involves an ancestral species splitting or branching into two descendant species. This is called cladogenesis. What matters most for speciation is that there is a barrier to gene flow, which allows one species to split into two.

How did species get where they are? Possible explanations:

1. Endemism: It evolved here and is only found in this region. 2. Range expansion: It evolved elsewhere (relatively nearby) and then expanded its range to also include this area. 3. Range shift: It evolved elsewhere and used to be found elsewhere, but its range shifted to include only the current distribution and not the former distribution. 4. Long-range dispersal / non-native / introduced / invasive: It arrived from somewhere else not nearby (e.g., Seeds transported by migratory birds? Introduced by humans?) 5. Vicariance: It evolved elsewhere, but then the physical landscape itself changed Woodlot = forest in a city

Lecture 10:

1. How do we assess biodiversity?

  • What is biodiversity?
  • How do we know how many species are in an area?
  • Species richness and relative abundance (evenness)
  • Comparisons across habitats 2. What determines species compositions and distributions?
  • Why are certain species found in a particular habitat?
  • What limits a species’ range? Abiotic and biotic factors
  • What happens when similar species overlap? 3. What determines how many individuals of a species there are?
  • Population growth
  • Population control
  • Distribution patterns within populations 4. What are the major patterns of biodiversity on a global scale?
  • Biomes, gradients, hotspots, and biogeographic regions
  • What factors determine this? 1. Gamma (γ) species diversity o Total number of species across all habitats being studied. 2. Beta (β) species diversity o Measure of how different the diversity is between two habitats. β‐diversity: A measure of how different diversity is between Habitat 1 and Habitat 2. β = (α H1 – Sc) + (α H2 – Sc ) α = Alpha Species Diversity H = Habitat Sc= Number of species common to both habitats

What determines species composition of a habitat? Local scale: Why don’t all three campus woodlots have the same species in them? Regional scale: Why are there different types of trees in southern versus northern Ontario? Global scale: Why doesn’t Ontario have the same species as Costa Rica? Species composition of a habitat:

  • Which species live in a particular habitat
  • Relative abundances of the species in the habitat
  • Spatial pattern of where the various species are located within the habitat Species distribution:
  • Where in the world a particular species lives (and where it doesn’t live)
  • Where the individuals of a particular species are located relative to each other within a population How did a particular species get there? **Three options:
  1. It evolved there (native / endemic).
  2. It moved there from somewhere else.**
  • Range shift
  • Range expansion
  • Long-range dispersal 3. Where “there” is has changed (vicariance). Dispersal ability and mechanism also affects species’distributions. Can involve eggs/seeds, larvae, juvenil es, or adults.
  • Water‐assisted
  • Wind‐assisted
  • Animal‐assisted

Abiotic vs. Biotic Factors Which factors limit the tree line? A. Underneath herbaceous canopy (shaded, competition for water) B. On bare soil (lots of light, no competition) C. On bare soil, surrounded by herbaceous canopy (lots of light, competition for water)

Lecture 12:

The Big Picture

1. How do we assess biodiversity?

  • What is biodiversity?
  • How do we know how many species are in an area?
  • Species richness and relative abundance (evenness)
  • Comparisons across habitats 2. What determines species compositions and distributions?
  • Why are certain species found in a particular habitat?
  • What limits a species’ range? Abiotic and biotic factors
  • What happens when similar species overlap? 3. What determines how many individuals of a species there are?
  • Population growth
  • Population control
  • Distribution patterns within populations 4. What are the major patterns of biodiversity on a global scale?
  • Biomes, gradients, hotspots, and biogeographic regions
  • What factors determine this? Population level variables
    • Abundance (N, number of individuals)
    • Density (N/area or N/volume)
    • Distribution (where they are)
    • Birth & Death rates (Δ N/time)
    • Sex & Age Structure (males vs. females)
    • Fecundity (# eggs produced per female)
    • Fertility (% of eggs that produce viable offspring)
    • Production (# offspring produced by a population)
    • Recruitment (# individuals reaching breeding age, includes offspring + immigration)

Lecture 13:

Why are similar fossils and living taxa found along the coasts of Australia, Africa, southern Asia and South America? Hypothesis 1: Through the 1800s, biogeographers struggled to explain the distributions of species like flightless birds on the basis of dispersal. Hypothesis 2: In 1912, Alfred Wegener (meteorologist) proposed the idea of Continental Drift, based on several observations:

**1. The shape of the continents suggested they fit together like a puzzle.

  1. Mountain chains, rock strata, glacial deposits, and fossils could be aligned.** ➢ 290 mya – Pangea (one continent). ➢ 200 mya – Laurasia & Gondwana separate. ➢ 140 mya – Gondwana begins to drift apart. ➢ 65 mya – Gondwana fully separated; Laurasia begins to drift apart. ➢ 50 mya – Continents near current positions.