E3

Question 1

What is a population?

Answer 1

Group of individuals of the same species that live within a particular area and interact with one another. Populations are dynamic entities that vary in size over time and space. Abundance can be reported as population size or density and can change over time and space, some species more than others

Question 2

What is dispersal?

Answer 2

A process in which individuals move away from a population in which they were born to another location where they will settle and reproduce. Species vary in ability to disperse. For most plants, dispersal occurs by seed movement, other species can disperse much farther.

Question 3

How may populations exist?

Answer 3

In patches that are spatially isolated but linked by dispersal. This can result from physical features of the environment and from human activities that subdivide populations

Question 4

What is an individual?

Answer 4

For some species, it is difficult to determine what an individual is. Aspen trees produce clones by forming new plants from root buds. Other plants form clones on horizontal stems or runners. Animals such as corals and anemones form clones. Some insects produce clones. Counting individuals in a population is tricky. Not all individuals in a pop are alike. Different life cycle stages : unitary organism - highly determinate ; fertilisation, birth, growth, maturity, reproduction, death. Modular organism - unpredictable form and growth ; develop according to environment.

Question 5

How can you count individuals?

Answer 5

Population boundaries, arbitrary boundary of study sites. Sticklebacks in lake, aphids on a leaf, pop densities.

Question 6

What is distribution and abundance effected by?

Answer 6

Habitat suitability, historical factors, dispersal. Abiotic factors. Species have varying tolerance ranges. Abiotic and biotic features of the environment can act together to determine distribution and abundance. Competition may also play a role. Some species depend on disturbance events which create opportunities. Evolution history, dispersal ability, geologic events all affect distribution.

Question 7

How does dispersal affect density of populations?

Answer 7

Many species of aphids produce winged forms in response to crowding. Desert pupfish in experimental open and closed pools. Open pools less overcrowding and mortality and higher reproductive rates. Dispersal also plays similar role in natural desert pupfish pops. Following heavy rains, the small pools are connected by temporary streams. Dispersal is risky but may provide a dish with greater chance for reproduction and survival

Question 8

What is a geographic range?

Answer 8

The whole range over which a species is found. Many species have a patchy distribution of populations across their geographic range. Some have dense pops whilst some have very large geographic ranges. Few species are on all continents. The geographic range includes all areas occupied by all life stages of a species. Some species migrate long distances between summer and winter. Patchy distribution may be due to unsuitable habitats. This can operate at different spatial scales. At large scales climate may dictate location, small scales soils, topography, other species can determine patchiness

Question 9

What is dispersion?

Answer 9

Spatial arrangement of individuals within a population. Regular - individuals are evenly spaced, random - scattered randomly, clumped - most common. Depends on location of essential resources, dispersal and behavioural interactions.

Question 10

How do you estimate abundance and distribution?

Answer 10

Complete counts of individual organisms are difficult. Several methods are used to estimate actual or absolute population size. Area-based counts are used to estimate abundance of immobile organisms. Quadrats used, individuals are counted in several quadrats the counts are used to estimate population size. Quadrats should be representative of the entire area covered by the population. As many quadrats as possible are used. Quadrats locations are selected at random or on a regularly spaced grid. Mark recapture methods used for mobile organisms, subset of individuals is captured, marked and released. At a later date, individuals are captured again, and the ration of marker to unmarked individuals is used to estimate population size. M (marked), C (captured post marking) R (recaptured individuals) N = M x C / R

Question 11

What are organisms life histories?

Answer 11

All organisms produce offspring but the size and number of offspring vary greatly. A record of events relating to growth, development, reproduction and survival of an organism. Defining characteristic are age and size at sexual maturity, amount and timing of reproduction, survival and mortality rates. Individuals within a species show variation in life history traits due to genetic variation or enviro conditions.

Question 12

What does natural selection favour?

Answer 12

Individuals whose life history traits improve their survival and chance of reproduction.

Question 13

What is phenotypic plasticity?

Answer 13

One genotype may be produce different phenotypes under different environmental conditions. Phenotypic plasticity may produce a continuous range of growth ; or discrete types - morphs

Question 14

What is polyphenism?

Answer 14

A single genotype produces several distinct morphs. Some tadpoles have both omnivore morphs and larger carnivore morphs. Carnivore tadpoles grow fast and metamorphose early. The omnivores grow more slowly, metamorphose in better conditions and have better chances of survival

Question 15

What complex modes or reproduction are there?

Answer 15

Asexual reproduction - prokaryotes and many protists
Sexual reproduction - promotes genetic variation, but population growth slower, isogamy (equal gametes), anisogamy (unequal gametes)

Question 16

What do most multicellular organism produce?

Answer 16

Anisogametes, complex life cycles involve at least two dinsticht stages (different body forms and habitats), transition between stages may be abrupt, most vertebrates have simple life cycles without abrupt transitions, but complex life cycles are common in insects, marine invertebrates amphibians, and some fish.

Question 17

What can reproductive patterns be classified along?

Answer 17

Several continua, semelparous - a single, distinct reproductive period then death, iteroparous - several reproductive events then death.

Question 18

What semelparous species are there?

Answer 18

Annual plants, agave vegetative growth can last up to 25yrs, giant pacific octopus.

Question 19

What iteroparous species are there?

Answer 19

Trees, most large mammals, several reproductive events.

Question 20

What are the r-selection and k-selection?

Answer 20

Two ends of a continuum of reproductive patterns. The r-K continuum is a spectrum of population growth rates, from fast to slow. r - short life spans, rapid development, early maturation, low parental investment, high rates of reproduction. K - long lived, develop slowly, delayed maturation, invest heavily in each offspring, and low rates of reproduction

Question 21

What are r and K?

Answer 21

r is the intrinsic rate of increase of a population, r-selection is selection for high population growth rates ; in unstable habitats, less crowded niches. K is the carrying capacity for a population. K-selection is selection for slower growth rates in populations that are at or near K ; crowded conditions, heavy investment in few offspring.

Question 22

What are trade-offs?

Answer 22

They shape and constrain life history evolution. Organisms allocate limited energy or resources to one structure or function at the expense of another. The larger an organism investment in each individual offspring the fewer offspring produced. Investment includes energy, resources, time, loss of chances to engage in alternative activities such as foraging. Clutch size can be limited. Clutch size greater at higher latitudes. Longer daylight allows for more foraging allowing larger clutch size.

Question 23

What are trade-offs in respect to species without parental care?

Answer 23

In species without parental care, reproductive investment is measured as resources invested in propagules, size of the propagule is a trade off with the number with the number produced. In plants seed size is negatively correlated with number of seeds produced.

Question 24

With trade offs under what conditions should an organism allocate energy to growth rather than reproduction?

Answer 24

Long life span, high adult survival rates, increased fecundity with body size. If rates of adults survival is low, early reproduction rather than growth would be favoured.

Question 25

What is senescence and how is it related to trade offs?

Answer 25

Senescence - decline in fitness of an organism with age and physiological deterioration. Can set an upper limit for reproduction. Semelparous species undergo very rapid senescence and date following reproduction. Senescence may occur earlier in populations with high mortality rates due to disease or predation. In some large social mammals post reproductive individuals contribute to the success of the group through parental and grandparental care.