Mechanisms of Population Change

Question 1

Selective Pressures

Answer 1

organisms over time change as a response to changes in their ecosystem.

Question 2

Adaptation

Answer 2

variations which assist in the survival of an organism that can be passed on by reproduction to offspring.

Question 3

Natural Selection

Answer 3

Individuals inherit traits that allow them to survive environmental conditions and then pass this to their offspring. Referred to by Darwin and “survival of the fittest”. These traits are passed on to offspring,

Question 4

3 broad categories of adaptation

Answer 4

(1) Structural - structure of organism changes
(2) Physiological - body functioning changes; ex. enzymes
(3) Behavioural - nerve control in mammals and hormone control in plants

Question 5

How can mutations pass on to offspring?

Answer 5

only if they occur to the DNA of gametes.

Question 6

Selective Advantage

Answer 6

mutations leading this may allow an organism to survive its environment when it otherwise would not have. (Like mutations that lead to the resistance to insecticides)

Question 7

What is required for species to survive selective pressure?

Answer 7

there must exist variations amongst the species - due to genetic variations which exist or mutations which occur to organisms genes (otherwise a monoculture would never survive)

Question 8

Artificial selection

Answer 8

when humans choose the traits they want to see in organisms.

Question 9

For natural selection to occur, there must be…

Answer 9

(1) already existing genetic variations in the species
(2) a selective pressure that causes some to die and some to survive.
(3) reproduction through those that survive in order to pass the genetic variation that gave you the advantage.

Question 10

Buffon (1707 - 1788)

Answer 10

• noted similarities between humans and apes
• suggested Earth was older than 6000 years
• challenged the idea that life forms are unchanging

Question 11

Carl Linnaeus (1707 - 1778)

Answer 11

• considered the father of taxonomy
• soley based his divisions on reproductive organs
• developed the binomial nomenclature

Question 12

Cuvier (1769 - 1832)

Answer 12

• considered the father of paleontology.

- discovered that fossils hidden in sedimentary rock could tell us about the past.

Question 13

Lyell (1797 - 1875)

Answer 13

• rejected Cuvier’s idea of natural disasters
• theorized that the geologic process actually operated slowly, and that the changes happened over a long period of time
• Inspired Darwin

Question 14

Lamarck (1744 - 1829)

Answer 14

• observed what her interpreted as the “line of descent”
• believed that offspring inherited traits
• believed that traits could be willed into being
• coined the use/disuse theory

Question 15

Thomas Malthus (1800’s)

Answer 15

• great influence on Darwin
• said populations would grow exponentially forever, but because of limited resources (food, shelter, etc) the population does not increase because of starvation, disease, etc. and the size reaches a carrying capacity for the given ecosystem.

Question 16

Wallace (1823 - 1913)

Answer 16

similar ideas to Darwin, but was never published.

Question 17

Darwin (1809 - 1882)

Answer 17

• accepted that populations changed over time
• discovered “natural selection”
• reasoned that this occured because of competition for limited resources
• that present forms of life have arisen by descent and modification from ancestral species
• survival of the fittest, and that natural selection made species better adapted to their local environments over time

Question 18

7 Evidences to evolution

Answer 18

(1) Fossil Records
(2) Transitional fossils
(3) patterns of distribution (geological distribution)
(4) comparative anatomy
(5) embryology
(6) molecular biology
(7) genetics

Question 19

Transitional fossils

Answer 19

fossils which show intermediary links between groups of organisms –> links today’s species to past fossil records

Question 20

Patterns of Distribution (geological distribution)

Answer 20

the way the continents moved and were once connected, and how climate change affected the changes in plants and animals.

Question 21

Convergent evolution

Answer 21

over time, similar forms develop in geographically different areas due to similar environments

Question 22

Divergent evolution

Answer 22

mutations and adaptations to changing environments causes the development of new species from a parent species

Question 23

Intraspecific competition

Answer 23

competition between the same species

Question 24

Interspecific competition

Answer 24

competition between different species

Question 25

homologous structures

Answer 25

can be similar in structure function or both, but come from the same common ancestor

Question 26

analogous structures

Answer 26

structures in organisms that have similar functions, but came from different ancestors.

Question 27

Molecular biology vs genetics

Answer 27

molecular biology is the study of molecules, and we can compare them among organisms. Genetics allows us to compare DNA and see the similarities, and also shows us how traits are passed to offspring.

Question 28

Speciation

Answer 28

the formation of a new species

Question 29

Transformation

Answer 29

mutations and adaptation to a changing environment over a long period of time results in a new species taking over

Question 30

Divergence

Answer 30

one or more species arise from a parent species that still exists

Question 31

For speciation to occur, two population have to be prevented from interbreeding. This can occur in two ways:

Answer 31

(1) geographical barriers
- something that separates two groups of the same species
(2) Biological barriers
- things altering their biology (ex, time of year they reproduce)

Question 32

Prezygotic Barriers

Answer 32

mechanisms that prevent the fusion of the egg and the sperm so that no zygote can form.

Question 33

Prezygotic barriers include:

Answer 33

(1) Habitat isolation
(2) Behavioural isolation
(3) Temporal isolation
(4) Mechanical isolation
(5) Gametic isolation

Question 34

Postzygotic Barriers

Answer 34

mechanisms that prevent a zygote from developing into a fertile adult offspring.

Question 35

Postzygotic barriers include:

Answer 35

(1) Reduced hybrid variability
(2) Reduced hybrid fertility
(3) Hybrid breakdown

Question 36

Habitat Isolation

Answer 36

when two closely related species live in entirely different habitats, they will seldom encounter each other and therefore there will be few opportunities to mate

Question 37

Behavioural Isolation

Answer 37

each species may use different signals to attract a mate. If one species does not recognize that signals of the other, the two species will not mate.

Question 38

Temporal Isolation

Answer 38

if two species breed at different time of the day or in different seasons, they cannot mix their gametes because when one species is ready to breed, the other is not.

Question 39

Mechanical Isolation

Answer 39

many species cannot mate because their reproductive anatomies are incompatible

Question 40

Gametic Isolation

Answer 40

this mechanism is due to the incompatibly of sperm and eggs from different species. The gametes do not fuse because they do not recognize each other.

Question 41

Reduced Hybrid Viability

Answer 41

genetic incompatibility between the two species may abort the development of the embryo at an early stage

Question 42

Reduced Hybrid Fertility

Answer 42

if two species can produce hybrid offspring that are viable, reproductive isolation is intact if these offspring are sterile and cannot breed

Question 43

Hybrid Breakdown

Answer 43

when some species cross mate, the first generation of offspring is viable and fertile. However, when these hybrids mate with each other or with either of the parent species, offspring of the next generation are feeble or sterile.