Reproductive Strategies

Objective: I will evaluate the effects of reproductive strategies and

compare them to carrying capacity.

Factors that Influence Population Size

•Density-dependent factors- the size of the population will influence an individual’s probability of survival.

•Density-independent factors- the size of the population has no effect on the individual’s probability of survival.

Exponential Growth Model

•Growth rate- the number of offspring an individual can produce in a given time period, minus the deaths of the individual or offspring during the same period.

•Intrinsic growth rate- under ideal conditions, with unlimited resources, the maximum potential for growth.

Exponential Growth Model

• J-shaped curve- when graphed the exponential growth model looks like this.

Logistic Growth Model

• Logistic growth- when a population whose growth is initially exponential, but slows as the population approaches the carrying capacity.

• S-shaped curve- when graphed the logistic growth model produces an “S”.

Variations of the Logistic Model•If food becomes scarce, the population

will experience an overshoot by becoming larger than the spring carrying capacity and will result in a die-off, or population crash.

Sexual Reproduction: Courtship

•Courtship rituals consume time and energy, can transmit disease, and can inflict injury on males of some species as they compete for sexual partners.

Figure 8-8

Reproductive Strategies

•K-selected species- the population of a species that grows slowly until it reaches the carrying capacity. Ex. elephants, whales, and humans.

•R-selected species- the population of a species that grows quickly and is often followed by overshoots and die-offs. Ex. mosquitoes and dandelions

Reproductive Patterns:Opportunists and Competitors•Large number of

smaller offspring with little parental care (r-selected species).

•Fewer, larger offspring with higher invested parental care (K-selected species).

Figure 8-9

Types of Population Change Curves in Nature•Population sizes may stay the same,

increase, decrease, vary in regular cycles, or change erratically.•Stable: fluctuates slightly above and

below carrying capacity.•Irruptive: populations explode and then

crash to a more stable level.•Cyclic: populations fluctuate and regular

cyclic or boom-and-bust cycles.•Irregular: erratic changes possibly due to

chaos or drastic change.

PREDATION

•Some prey escape their predators or have outer protection, some are camouflaged, and some use chemicals to repel predators.

Figure 7-8

Fig. 7-8a, p. 153(a) Span worm

Camouflage

Fig. 7-8b, p. 153

(b) Wandering leaf insect

Camoufla

ge

Fig. 7-8c, p. 153(c) Bombardier beetle

Chemical Warfare

Fig. 7-8d, p. 153(d) Foul-tasting monarch butterfly

Chemical Warfare

Fig. 7-8e, p. 153(e) Poison dart frog

Warning

Coloration

Fig. 7-8f, p. 153(f) Viceroy butterfly mimics monarch butterfly

Mimicry

Fig. 7-8g, p. 153

(g) Hind wings of Io moth resemble eyes of a much larger animal.Deceptive Looks

Fig. 7-8h, p. 153

(h) When touched, snake caterpillar changes shape to look like head of snake.

Deceptive Behavior