BIOL 1070: MIDTERM LECTURE NOTES
i. 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
ii. 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?
iii. What determines how many individuals of a species there are?
• Population growth
• Population control
• Distribution patterns within populations
iv. 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)
, Population abundance Pt2 = Pt1 + (B – D) + (I – E)
Spatial Patterns of Distribution:
• Clumped
• Even
• Random
• Density-dependent factors: factors affect per capita birth or death rates in a way that
depends on population density (i.e., the effect is stronger/weaker depending on whether
the population is dense/sparse).
Density-independent factors: factors affect per capita birth or death rates in a way that does
NOT depend on population density
• Density independent factors can
intensify the effects of density-dependent
factors
– e.g., a hard freeze diminishes the supply
of food or prey
Giant Hogweed (Heracleum mantegazzianum)
• Grows along roadsides, ditches, and streams
• Invades old field and open woodlands
• Seeds viable for up to 15 years
• Produces winged seeds that can float for three days or ‘fly’ in the wind up to 10 metres
i. 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
ii. 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?
iii. What determines how many individuals of a species there are?
• Population growth
• Population control
• Distribution patterns within populations
iv. 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)
, Population abundance Pt2 = Pt1 + (B – D) + (I – E)
Spatial Patterns of Distribution:
• Clumped
• Even
• Random
• Density-dependent factors: factors affect per capita birth or death rates in a way that
depends on population density (i.e., the effect is stronger/weaker depending on whether
the population is dense/sparse).
Density-independent factors: factors affect per capita birth or death rates in a way that does
NOT depend on population density
• Density independent factors can
intensify the effects of density-dependent
factors
– e.g., a hard freeze diminishes the supply
of food or prey
Giant Hogweed (Heracleum mantegazzianum)
• Grows along roadsides, ditches, and streams
• Invades old field and open woodlands
• Seeds viable for up to 15 years
• Produces winged seeds that can float for three days or ‘fly’ in the wind up to 10 metres
