Biology Unit 2

Chapter 4B,C
Ecological species model: based on the ecological niche occupied by an organism
Disadvantage: a very general way as niche definitions vary and many species
occupy more than one niche
Mate-recognition model: a concept based on unique fertilization systems
including mating behavior:
Disadvantage: many species will mate with or cross pollinate other species and
may even produce fertile offspring, but are nevertheless different species.
Genetic species model: based on DNA evidence.
Disadvantage: people still have to decide how much genetic difference is needed
for two organisms to be members of different species.
Morphological species concept: based solely on the appearance of the organisms
involved
Disadvantage: organisms that show sexual dimorphism (great difference between
male and female) can be classified as different species.
Reproductive/biological species model: a group of organisms with similar
characteristics that are all potentially capable of breeding produce a fertile
offspring:
Disadvantage: not the best for plants
Q: What are the limitations of species models?

Ans:
1. Finding the evidence for new species, which is expensive, time consuming and
may not prove anything.
2. Plants of different but closely related species frequently interbreed and produce
fertile hybrids, when should hybrids be regarded as a separate species?
3. Many organisms do not reproduce sexually.
4. Fossil organisms cannot reproduce

Diversity index:

High biodiversity is seen in:

1. Very stable ecosystems
2. Areas where there are high levels of productivity
3. Areas where organisms can grow and reproduce rapidly
Q: What is the effect of introduction of new species in habitat?

Answer: The new incoming organism can become established very rapidly and
overpower an existing species if they are competing for food or territory.
Q: In less hostile environments, biodiversity can be very high, why?
Answer: this results in a very stable ecosystem, because new species moving in or
out will have almost no effect
Q: What causes biodiversity to decrease?
Answer: Biodiversity can be lost due to natural events such as volcanic eruptions
or flooding, but also as a result of human activities.
BIODIVERSITY IS NOT CONSTANT. (hard to measure)
The gene pool of a species is all of the genes in the genome, including different
variant of each gene.
Mutation- good one
adaptation increases---survival increases---reproduces and pass on advantageous
allele---allele frequency ---gene pool increase and species evolves
Mutation- bad one
By natural selection---removes it from gene pool---allele frequency decreases

Heterozygosity index:

Endemism common--- rich biodiversity---low genetic diversity

Three types of adaptations:

1. Anatomical
2. Physiological
3. Behavioral
Conditions of the Hardy-Weinberg Equilibrium:
1. No mutations
2. There is random mating
3. The population is large
4. The population is isolated
5. There is no selection pressure (no evolving and no speciation)
Variation---adaptations---selection pressure---natural selection—evolving---
speciation
No gene pool---gene pool different---selection pressure different---natural selection
is different---speciation---no more breeding
Q: What is the most important factor in the process of speciation?
Answer: Reproductive isolation and reduced gene flow
Can also occur as a result of hybridization
Q: ways in which organisms become reproductively isolated?
1. Geographical isolation (separated by a physical barrier)
2. Ecological isolation (occupy different parts of the habitat)
3. Season isolation (sexual receptiveness becomes different)
4. Behavioral isolation (could be due to a mutation)
5. Mechanical isolation (changes in genitalia or changes in relationship of
stigma and stamen)

Two types of speciation

1. Allopatric
2. Sympatric

Allopatric speciation--- physical barrier due to which organisms don’t breed

leading to development of new species.

Sympatric speciation---Mutation that does not allow successful reproduction

leading to the development of new species

Allopatric speciation is followed by adaptive radiation

Adaptive radiation occurs when one species develops rapidly to from several
different species, all which fill different ecological niches.
Q: Give two examples of adaptive radiation
Answer:
1. Australian Monotremes and Marsupials
Monotremes---lay eggs and have mammary glands
Marsupials---give birth to immature youngs which continue do develop in external
pouch (kangaroos)
Placental mammals---develop placenta inside, have a womb for growth and
development of young.

2. Drawin’s Finches

evolved through natural selection due to different feeding niches.

Variation in beak size/shape---access different types of food---specific food

sources---better---survived, reproduces, passing on advantageous traits

Food availability acted as a major selection pressure.

Q: Give an example of sympatric speciation

Answer: Population bottlenecks

The effect of an event or series of events that dramatically reduces the size of a
population resulting in large changes in allele frequences and a reduction in genetic
diversity.

Q: Explain the founder effect?

Answer: The loss of genetic variation that occurs when a smaller number of
individuals become isolated, forming a new population with allele frequences not
representative of the original population.
Q: What is conservation

Conservation means keeping and protecting a living and changing environment.

Two types of conservations:

1. Ex-situ conservation (zoos/seeds banks)

2. In-situ conservation (in natural habitat)

Q: What is ex-situ conservation?

Answer: Remove some of the animals or plants from their natural habitat, this
enables genetic material to be conserved and at best a breeding population can
eventually be returned

Occurs in a country where threatened species originates

Q:What are the techniques of ex-situ conservation

Answer:

1. Cross-breeding crop plants back to original wild plants or using wild plants to
supply genes for genetic engineering.
2. Botanic gardens has plants itself which maintain collections many of the
worlds most interesting and unusual plants.
3. Using a seed bank

Q: How are seeds conserved in a seed bank?

Live seeds are collected from the wild, removed from the fruits and cleaned. They
are screened using X-rays to be sure that they contain fully developed embryos.
Then they are dried, piyt into jars and stored at temperatures below 0 (-20 and -40).
Many will survive and remain capable of germinating for up to 200 years.

Q: Advantages of seed banks?

Answer: Seeds are usually small so many can be stored cheaply in a small space.

Seeds contain all the genetic material of the plant, so they are a record of the
genetic makeup of the species as well as a potential new plant for future

Q: Disadvantages of seed banks?

Seeds of some species do not store well

These need to be grown in their natural habitats, field gene banks which take up a
lot of room and work

Q: Explain the ex-situ conservation of animals:

Use captive breeding programs

Individuals of an endangered species are bred in zoos and parks in an attempt to

save the species from extinction.

Ultimate goals is to reintroduce the captive bred animals into wild to restore the
original population

Q: Challenges of captive-breeding programs

Answer:

Not enough space/sufficient resources in zoos for all

Often difficult to provide the right conditions for breeding

Reintroduction to wild will be unsuccessful unless original reason for species being
pushed to extinction is removed.

Animals bred in captivity may have great problems adjusting to unsupported life in
wild
Time consuming

Small population so gene pool small which causes serious problems