Ecology: Population Ecology

2 POPULATIONS 3. A population is a group of individuals of the same species living in an area

DISTRIBUTION PATTERNS Uniform distribution results from intense competition or antagonism between individuals. Random distribution occurs when there is no competition, antagonism, or tendency to aggregate. Clumping is the most common distribution because environmental conditions are seldom uniform. 3 Populations disperse in a variety of ways that are influenced by environmental and social factors

Fig. 52.1, Campbell & Reece, 6 th ed. Clumped distribution in species acts as a mechanism against predation as well as an efficient mechanism to trap or corner prey. It has been shown that larger packs of animals tend to have a greater number of successful kills. What causes these populations of different organisms to clump together?

POPULATION DISPERSAL In rare cases, long-distance dispersal can lead to adaptive radiation For example, Hawaiian silverswords are a diverse group descended from an ancestral North American tarweed 5

THE SPREAD OF THE AFRICANIZED HONEY BEE WHEN DID THEY FIRST ARRIVE IN THE AMERICAS? HOW LONG DID IT TAKE FOR THEM TO EXPAND THEIR RANGE INTO THE US? HOW CAN YOU EXPLAIN THEIR SUCCESS IN EXPANDING THEIR TERRITORY? 6

SMALL GEOGRAPHIC RANGE 7

SPECIES WITH A LARGE GEOGRAPHIC RANGE 8

9 ESTIMATING POPULATION SIZE THE MARK-AND-RECAPTURE TECHNIQUE

ESTIMATING POPULATION SIZE THE MARK-AND-RECAPTURE TECHNIQUE 10

LET’S TRY AN EXAMPLE! 11

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13 WHICH METHOD WOULD YOU USE? 1. To determine the number of deer in the state of Virginia? 2. To determine the number of turkeys in a county? 3. To determine the number of dogs in your neighborhood? 4. To determine the number of ferrel cats in your neighborhood?

SURVIVORSHIP CURVES What do these graphs indicate regarding species survival rate & strategy? Human (type I) Hydra (type II) Oyster (type III) Percent of maximum life span Survival per thousand I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)

POPULATION GROWTH CURVES 15 d = delta or change N = population Size t = time B = birth rate D =death rate

POPULATION GROWTH MODELS

EXPONENTIAL GROWTH CURVES 17 d = delta or change N = Population Size t = time r max = maximum per capita growth rate of population Population Size, N Time (hours) Growth Rate of E. coli

LOGISTIC GROWTH CURVES 18

LOGISTIC GROWTH CURVES 19 d = delta or change N = Population Size t = time K =carrying capacity r max = maximum per capita growth rate of population

COMPARISON OF GROWTH CURVES 20

GROWTH CURVE RELATIONSHIP 21

EXAMINING LOGISTIC POPULATION GROWTH 22

EXAMINING LOGISTIC POPULATION GROWTH 23 Hypothetical Example of Logistic Growth Curve K = 1,000 & r max = 0.05 per Individual per Year

POPULATION REPRODUCTIVE STRATEGIES r-selected (opportunistic) Short maturation & lifespan Many (small) offspring; usually 1 (early) reproduction; No parental care High death rate K-selected (equilibrial) Long maturation & lifespan Few (large) offspring; usually several (late) reproductions Extensive parental care Low death rate

25 Some populations overshoot K before settling down to a relatively stable density Some populations fluctuate greatly and make it difficult to define K How Well Do These Organisms Fit the Logistic Growth Model?

Percent of population Rapid growth Afghanistan Slow growth United States No growth Italy Male Female Age –84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 Age –84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0– Age Structure Diagrams: Always Examine The Base Before Making Predictions About The Future Of The Population