2.1: species & populations

Question 1

species definition:

Answer 1

a group of living organisms, sharing common characteristics that interbred and produce fertile offspring.

Question 2

habitat definition:

Answer 2

environment in which a species lives

Question 3

niche:

Answer 3

the particular set of abiotic and biotic conditions and resources to which an organism or population responds

Question 4

two forms of niches;

Answer 4

fundamental: full range of conditions and resources in which a species survives and reproduces

realised: actual conditions in which a species exists due to biotic interactions

Question 5

biotic egs. of niches -

Answer 5

• where it lives
• relations
• how it responds to resources available
• how much space there is
• availability of light & water

Question 6

diff b/w abiotic & biotic -

Answer 6

abiotic - non-living physical factors:
- temperature
- soil salinity
- PH
- sunlight
- precipitation

biotic - interactions b/w the organisms:
- predation
- parasitism
- mutualism
- competition

Question 7

population definition:

Answer 7

a group of organisms of the same species, living in the same area at the same time, which are capable of inter-breeding.

Question 8

how a scientific name is composed -

Answer 8

1. genus name
2. species name

for eg. Homo sapiens

Question 9

population density:

Answer 9

average number of individuals in a stated area

Question 10

factors affecting population size -

Answer 10

• birth rate
• death rate
• migration (immigration & emigration)

Question 11

limiting factors:

Answer 11

factors which slow down the growth of a population as it reaches its carrying capacity

Question 12

carrying capacity:

Answer 12

the maximum number of a species that can be sustainably supported by an area

Question 13

egs of limiting factors -

Answer 13

• limited phosphate in aquatic systems
• low temperature in the tundra which freezes the soil and limits water availability to plants

Question 14

population dynamics:

Answer 14

study of the factors that cause changes to population sizes

Question 15

population interactions -

Answer 15

• competition
• predation
• herbivory
• parasitism
• mutualism

Question 16

competition:

Answer 16

when any resource in an ecosystem exists only in a limited supply, competition takes place

Question 17

two types of competition;

Answer 17

intra-specific competition: between members of the same species

inter-specific competition:
different species competing for the same resource

Question 18

predation:

Answer 18

when one animal (the predator) eats another animal (the prey)

eg. lions eating zebras

Question 19

herbivory:

Answer 19

an animal (herbivore) eating a green plant

some plants have defence mechanisms against this. for eg. thorns on a cacti

Question 20

parasitism:

Answer 20

relationship b/w two species, in which one species (the parasite) lives in or on another (the host) gaining its food from it

eg. vampire bats

Question 21

mutualism:

Answer 21

relation between two or more species, in which all benefit and none suffer. form of symbiosis.

eg. lichen & green algae - where the fungus benefits from obtaining sugars from the algae and the algae benefits from minerals and water from the fungus.

leguminous plants and nitrogen fixing bacteria. bacteria gets shelter in the plant while the plant gets nitrogen in the form of ammonium compounds.

Question 22

symbiosis:

Answer 22

living together

• mutualism
• parasitism
• commensalism

Question 23

commensalism:

Answer 23

when one partner is helped and the other is not significantly harmed.

eg. orchid or fern growing halfway up a tree trunk

Question 24

what do no limiting factors lead to?

Answer 24

exponential or geometric growth.

Question 25

S & J population curves:

Answer 25

generalised response of populations to a particular set of conditions; abiotic and biotic factors.

Question 26

S curves:

Answer 26

starts [lag phase] w. exponential growth - [exponential phase] (due to no limiting factors)

however, above a certain population size, the growth rate slows down gradually.

finally, resulting in a population of constant size. [stationary phase]. this is when the carrying capacity has been reached.

Question 27

environmental resistance -

Answer 27

area between the exponential growth curve and the S curve is called environmental resistance

Question 28

J curve:

Answer 28

population grows exponentially at first and then collapses [die-back]. population exceeds carrying capacity before the collapse [overshoot]

typical of microbes, fishes, and small mammal populations.