Part 3 Topic D Flashcards
external fertilization
fertilization that takes place outside the body of the female; in aquatic organisms, for example, eggs and sperm are released into the water
internal fertilization
fertilization that takes place inside the body of the female
internal fertilization is an adaption for…
living on land, prevents gametes from drying out (some marine animals reproduce this way too)
external fertilization is generally associated with the release of….
large numbers of gametes and the production of large numbers of offspring (each has a lower probability of survival)
internal fertilization typically produce….
fewer offspring and invest considerable time and energy into raising offspring
r-strategist
a species that produces large numbers of offspring but provides few resources for their support
K-strategist
a species that produces relatively few young but invests considerable resources into their support
according to the model of r-stragetists and K-strategists, the environment places ______
selective pressures on organisms to drive them in one or the other direction
what environment did r-strategists evolve in?
unstable, changing, and unpredictable environments; advantage of reproducing quickly and producing many offspring
what environment did K-strategists evolve in?
stable, unchanging, and predictable environments; more crowding and larger populations; intense competition for limited resources so increased parental care and few offspring are favoured
age structure
the number of individuals within each age group of a population
what do ecologists use to understand past and predict future changes in populations?
ecologists use birth rates, expected longevity of individuals, and the proportion of individuals in a population that is able to reproduce
estimating the number of individuals of differing ages enables ecologists to predict….
whether the size of a population will increase or decrease
a growing population has what shaped distribution?
pyramid shaped distribution, larger young class than older class
a stable population has a ______ distribution of age classes
even
in humans, differences in age structures reflect….
socioeconomic variation among countries
differences in age structure in other species reveal…
threats from various sources
survivorship curves record changes in…
survival probability over an organism’s life-span
demography
the study of the size, structure, and distribution of populations over time, including changes in response to birth, aging, migration, and death
cohort
a group of the individuals born at a given time (usually group that we begin our studies with)
life table
a table that presents information about how many individuals of a cohort are alive at different points in time (used to identify patterns of survival in population)
survivorship
the proportion of individuals from an initial cohort that survive to each successive stage of the life cycle
populations differ in the ages at which they experience the most ______
mortality
survivorship curve Type I
most humans and other large mammals survive their early years and show a steep decline in the last part of their life-span
survivorship curve Type II
small mammals and birds tend to lose numbers steadily throughout their lives
survivorship curve Type III
many Turtle Grass seedlings and those of most other herbaceous plants DO NOT SURVIVE THE EARLIEST PERIOD of life, but those that do survive show only slow additional declines over time
associate r-strategists with…
Type III survivor: r-strategists reproduce at rates approaching r, the intrinsic rate of growth
associate K-strategists with…
Type I survivor: population densities commonly lie near the carrying capacity K, when resources become scarce
r-strategists and K-strategists are on opposite ends of:
extremes-possible reproduction strategies in between can exist
life history
the typical patter of resource investment in each stage of a given species’ lifetime
control over allocation of energy resources involves :
physiological trade-offs
the various ways in which animals and plants allocate resources to growth and reproduction is rooted in their:
physiological and their physiological traits are themselves, evolved traits
