2.1 Species and Populations

Question 1

Define species

Answer 1

a group of organisms that share common characteristics and that interbreed to produce fertile offspring.

Question 2

Define habitat

Answer 2

The environment in which a species normally lives

Question 3

Define niche

Answer 3

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

Question 4

Distinguish between biotic and abiotic (physical) components of an ecosystem​

Answer 4

The main difference between biotic and abiotic factors is that biotic factors are comprised of living things (such as plants, animals, and fungi). In contrast, abiotic factors are comprised of non-living chemical and physical environmental conditions in an ecosystem (such as wind, water, and light).

Question 5

Distinguish between fundamental and realized niche with reference to a named example

Answer 5

Fundamental niche: theoretical niche, which describes the full potential of where, when and how a species can exist

realised niche: where the species actually exists

Question 6

List the significant abiotic (physical) factors of an ecosystem.​

Answer 6

The chemical and physical factors in an ecosystem (non living) for example: temperature, moisture, salininty, soil type, light, air

Question 7

limiting factors definition

Answer 7

factors that limit the growth of populations. they will slow the growth of a population as it approaches the carrying capacity of the system

Question 8

limiting factors example

Answer 8

for animals: lights, nutrients, water, carbon dioxide, and temperature.

for animals: space, food, mates, nesting sites, and water.

Question 9

define predetation

Answer 9

when one animal (or occasionally a plant) hunts and eats another organism

Question 10

define herbivory

Answer 10

an organism that feeds off of plants. type of predation

Question 11

define parasitism

Answer 11

a symbiotic relationship in which one species benefits at the expense of another

Question 12

define mutualism

Answer 12

A type of symbiotic relationship in which both species benefit from the relationship.

Question 13

define disease

Answer 13

a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism. includes organisms such as viruses, bacteria, fungi and parasites that cause disease.

Question 14

define competition

Answer 14

the demand by individuals for limited enviornmental resources

within species: intraspecific competition
between different species: interspecific competition

Question 15

define symbiosis

Answer 15

species live together which can include parasitism, mutualism, and commensalism.​

Question 16

Density-dependent factors

Answer 16

Factors that lower the birth rate or raise the death rate as a population grows in size. They are negative feedback mechanisms leading to the stability or regulation of the population.
When prey increases so does the predator, but when this occurs the prey decreases and then again the predators decrease too causing the prey to increase again.

Question 17

Density-independent factors

Answer 17

Factors that affect a population disregarding population density

Question 18

Factors which regulate population size can be divided into either INTERNAL or EXTERNAL

Answer 18

Internal: fertility rates, territory sizes
External: predation, pressure, parasitism

Question 19

Ways humans can cause population growth

Answer 19

• increase available resources
• reduce competition
• reduce pressure from predators
• introduce animals to new areas

Question 20

Ways humans decline population

Answer 20

• change environment, cause habitat disruption
• change the biological environment by introducing new species
• cause secondary extinctions
• overkill

Question 21

define population

Answer 21

a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.

Question 22

Factors affecting population size

Answer 22

• natality
• mortality
• migration (immigration or emigration)

Question 23

Define/describe s curve

Answer 23

when a graph of population growth is plotted against time.

it shows initial rapid growth (exponential growth), but then slows down as the carrying capacity is reached.

4 stages:
1. lag phase: pop numbers are low leading to low birth rates
2. exponential growth phase: pop grows at an increasingly rapid rate
3. transitional phase: pop growth slows down considerably although continuing to grow
4. stationary phase: pop growth stabilises (graph flattens) and then pop fluctuates around a level that represents the carrying capacity

Question 24

Define/describe j curve

Answer 24

exponential growth is an increasing or accelerating rate of growth.

growth is initially slow, but becomes increasingly rapid and does not slow down as population increases.

Question 25

Explain the concepts of limiting factors and carrying capacity in the context of population growth​

Answer 25

Populations have an upper level or exent to numbers that can be sustained in a given enviornment - carrying capacity. The carrying capacity represents the population size at which enviornmental limiting factors limit further population growth. The CC is affected by various limiting factors including the availability of food and water, territorial space, predetation, disease and availability of mates

Question 26

Explain population growth curves in terms of numbers and rates

Answer 26

• Rapid increase in population growth due to high natality exceeding mortality, with abundant resources and few predators or diseases.
• Growth begins to slow as resources diminish, and the mortality rate rises due to increased competition, predators, and diseases.
• Population size stabilizes as natality equals mortality, influenced by resource scarcity and other limiting factors, maintaining a balance around the environment’s carrying capacity.

Question 27

define carrying capacity

Answer 27

the maximum number of individuals of species that can be sustained by an environment. it represents the population size at which environmental limiting factors limit further population growth.

Question 28

compare/ contrast S versus J curves

Answer 28

COMPARE
- Both curves show how populations grow and reach a carrying capacity

CONTRAST
- The S-curve occurs in a limited environment, while the J-curve occurs in an unlimited environment
- The S-curve represents logistic growth, while the J-curve represents exponential growth
- The S-curve eventually levels off at the carrying capacity, while the J-curve continues to increase until a limiting factor is encountered
- The S-curve is more common in nature, while the J-curve is less common and is often observed in laboratory conditions