module 6 - 19.11 speciation & evolution

Question 1

what 2 principle criteria do biologists consider when classifying organisms as members of the same species?

Answer 1

• members of the same species share common physical characteristics and display similar biochemical, behavioural, and genetic features that differ from those of other species
• members of the same species interbreed and share a common gene pool and produce fertile offspring

Question 2

what is the definition of a species?

Answer 2

a group of organisms with similar anatomical and physiological features which can interbreed to produce fertile offspring and remain reproductively isolated from other species

Question 3

what is speciation?

Answer 3

• the formation of new species through the process of evolution
• the organisms belonging to the new species will no longer be able to interbreed to produce fertile offspring with organisms belonging to the original species

Question 4

what events happen leading to speciation?

Answer 4

• members of a population become isolated and don’t interbreed with rest of the population, so in no gene flow between the 2 groups
• alleles within the groups continue to do random mutations, the environment of each group may be different or change so different characteristics will be selected
• accumulation of mutations and changes in allele frequencies over many generations eventually lead to large changes in phenotype, members become so different that they no longer interbreed, so are reproductively isolated and are different species

Question 5

what is allopatric speciation?

Answer 5

• more common form of speciation and happens when some members of a population are separated from the rest of the group by a physical barrier e.g. river
• causes different physical adaptations

Question 6

how are Darwin’s Finches an example of allopatric speciation?

Answer 6

• a small group of finches from an original population flew and got stranded on different islands
• the finches have formed new colonies on different islands
• finches evolved and adapted to different environments (example of adaptive radiation)
• finches’ beaks are adapted to their environment and their food sources
• SEE PAGE 545-6 ON KERBOODLE

Question 7

what is adaptive radiation?

Answer 7

where rapid organism diversification takes place

Question 8

what is sympatric speciation?

Answer 8

• occurs within populations that share the same habitat
• more common in plants than animals
• can occur when members of 2 different species interbreed and form fertile offspring

Question 9

how is fungus-farming ants an example of sympatric speciation?

Answer 9

• fungus farming ants cultivate the growth of fungi by supplying organic material to keep the fungi growing
• parasitic ants spend their time eating fungi and reproducing
• genetic analysis shows parasitic ants are descendants of fungus-farming ants
• evolved within same habitat as result of change in behaviour

Question 10

what are reproductive barriers?

Answer 10

barriers to successful interbreeding can form within populations before or after fertilisation has occurred
- prezygotic reproductive barriers, often produced as a result of hybridisation, reduce reproductive potential of offspring

Question 11

what is disruptive reproduction?

Answer 11

• takes place when more extreme phenotypes (or genotypes) within a population have a fitness advantage over intermediate individuals
• in disruptive selection, the population is separated into different groups by an increase in traits variant

Question 12

what does polymorphic mean?

Answer 12

display more than one distinct phenotype

Question 13

what is artificial selection/selective breeding?

Answer 13

selection for breeding of plants or animals with desirable characteristics by farmers or breeders

Question 14

what are the problems caused by inbreeding?

Answer 14

• limiting the gene pool and decreasing genetic diversity reduces chances of a population of inbred organisms evolving and adapting to changes in their environment
• causes genetic disorders caused by recessive alleles e.g. cystic fibrosis
• organisms closely related are genetically similar and are likely to have the same recessive alleles - offspring have a higher chance of recessive traits and disorders

Question 15

What are seed banks?

Answer 15

Keep samples of seeds from both wild and domestic varieties

Question 16

What are gene banks?

Answer 16

Store biological samples over than seeds, such as sperm or eggs (are are usually frozen)

Question 17

What are alleles from gene banks used to do?

Answer 17

• Used to increase genetic diversity in a process cared outbreeding
• breeding unrelated a distantly related varieties is also a form of outbreeding

Question 18

What does outbreeding do?

Answer 18

Reduces occurrence of homozygous recessives and increases potential to adapt to environmental changes