Unit 3 - Populations PDF

Unit 3 - Populations Enduring Understanding: Populations change over time in reaction to a variety of factors 3.1 Specialist vs. Generalist Species Specialists: Smaller range of tolerance, or narrower eco...

Unit 3 - Populations Enduring Understanding: Populations change over time in reaction to a variety of factors 3.1 Specialist vs. Generalist Species Specialists: Smaller range of tolerance, or narrower ecological niche makes them more prone to extinction - Specific food requirements (bamboo) - Less ability to adapt to new conditions Generalists: Larger range of tolerance, broader niche makes them less prone to extinction & more likely to be invasive - Broad food req. - High adaptability GENERALISTS VS. SPECIALISTS “ Identify ONE characteristic of specialist species and explain how that characteristic makes them more likely to become extinct than generalist species. 6 7 3.2 K-selected & r-selected species Objectives, EKs, and Skills Reproductive Strategies: Quality vs. Quantity K-selected - “quality” ▰ Few offspring, heavy parental care to protect them ▰ Generally have fewer reproductive events than r-strategists ▻ Ex: most mammals, birds ▰ Long lifespan, long time to sexual maturity = low biotic potential = slow population growth rate ▻ More likely to be disrupted by environmental change or invasive species Quality vs. Quantity r-selected - “quantity” ▰ Many offspring, little to no parental care ▰ May reproduce only once, but generally reproduce many times throughout lifespan ▻ Ex: insects, fish, plants ▰ Shorter lifespan, quick to sexual maturity = high biotic potential = high population growth rate ▻ More likely to be invasive ▻ Better suited for rapidly changing environmental conditions Habitats/Populations K-selected: r-selected: ▰ Usually live in habitats with higher ▰ Usually live in habitats with lower competition competition for resources for resources ▰ Populations that reach carrying ▰ Population are more likely to fluctuate above capacity (K) usually remain at stable and below carrying capacity (overshoot and size, near K die-off) ▻ Hence, K-selected or K-strategist ▻ “r” is the variable used to represent maximum reproductive rate in ecology ▻ Hence, r-selected or r-strategist Traits or characteristics of r-selected & K-selected species 13 It’s a Spectrum Spectrum of Parental Care K-selected r-selected ▰ Low biotic potential (rep. rate) = hard for pop. ▰ High biotic potential (rep. rate) = more rapid pop. to recover after a disturbance (env. change) recovery after disturbance ▰ High parental care means death of parent = ▰ Low parental care means death of parent doesn’t death of offspring impact offspring ▰ Invasives (usually r) outcompete for ▰ Not as impacted by invasive species since their resources with high biotic potential & rapid pop. grow quickly pop. growth ▻ More likely to be the invasive ▰ Less likely to adapt & more likely to go extinct ▰ Larger pop. & faster generation time = higher chance of adaptation & lower chance of extinction Invasiveness & Disturbances 16 “ Identify ONE characteristic of an r-selected species that could increase the likelihood of the r-selected species becoming a more successful invasive species than K-selected species 17 Describe the relationship between Zebra Mussel and Unionid Mussel population density in the Hudson River 18 19 3.3 Survivorship Curves Objectives, EKs, and Skills  ★ Faster drop in line = quicker die-off of individuals ★ Slower drop in line = longer avg. lifespan Survivorship Curve: line that shows survival rate of a cohort (group of same-aged individuals) in a pop. from birth to death Type I, II, and III Survivorship Type I (mostly K-selected) Type III (mostly r-selected) ▰ High survivorship early in life due ▰ High mortality (low survivorship) early to high parental care in life due to little to no parental care ▰ High survivorship in mid life due to ▰ Few make it to midlife; slow, steady large size & defensive behavior decline in survivorship in mid life ▰ Rapid decrease in survivorship in ▰ Even fewer make it to adulthood; slow late life as old age sets in decline in survivorship in old age ▻ Ex: most mammals ▰ Ex: insects, fish, plants Type II (in between r & K) ▰ Steadily decreasing survivorship throughout life FRQ Practice 3.3 Describe the trend in survivorship shown in this graph. Justify which type of survivorship curve these data represent.