Chapter 18 Flashcards
Variation and Selection
What is Variation and its types?
Variation is the difference between individuals of the same species.
- It refers to observable differences within a species.
- They may be:
>Genetic
>Phenotypic
What is Genetic Variation?
- It is the difference in genetics among individuals of the same species.
ex: Blood group, eye colour, gender, ability to roll tongue.
It is inherited and determined by genes and cant be changed
What is Phenotypic variation?
It is the variation of phenotypes (observable traits) within a population.
- They can be determined by genes or environment, or a combination of both.
ex: Climate, diet
What factors cause genetic variation?
- Mutation
- Meiosis
- Random mating
- Random fertilisation
What is Continuous variation?
Continuous variation results in a range of Phenotypes (observable features) between 2 extremes
ex: Body mass, Body length (height and weight)
- This is caused by genes AND environment.
What is Discontinuous variation?
Discontinuous variation results in a limited number of Phenotypes with NO INTERMEDIATES (no ranges)
ex: sex, abo blood types, seed shape and color of peas.
- It is caused by GENES ONLY.
What types of graphs are used for Continuous and Discontinuous variation?
Continuous variation is plotted on a graph with smooth curves.
Discontinuous variation has specific options, it is plotted on bar graphs with distinct choices.
What is Mutation?
Mutation is spontaneous, genetic change where new alleles are formed.
What is Gene mutation?
Gene mutation is change in the base sequence of DNA.
It is a random change.
What factors increase rate of Mutations?
Exposure to chemicals and ionising radiation.(Mutagens)
How does chromosome mutation occur?
Chromosome mutation are results from damage, loss or gain of an extra chromosome.
How does gene mutation occur?
It is when one or more genes isn’t replicated correctly.
What is the difference between a mutation that occurs in a gamete and in a somatic cell?
- Mutation that occurs in a GAMETE affects ALL CELLS of the individual of that zygote.
- Mutation that occurs in a SOMATIC CELL only affects the cells further produced by mitosis of that affected cell.
What is an Adaptive feature?
An Adaptive feature is an inherited feature that helps an organism survive and reproduce in its environment.
What are the adaptive features of a Polar bear?
- Small ears reduce heat loss.
- 10cm layer of fat (blubber) for insulation.
- thick coat with long loosely packed hair, and a dense layer of short hair, forming an insulating layer.
- Long hairs are water repellent and oily, allowing the bear to shake off water.
- Has black skin underneath to absorb heat.
- White fur acts as camouflage.
- Little warm blood circulates to the surface of skin, reducing heat loss. (SMALL BLOOD SUPPLY)
What are the adaptive features of a Camel?
- Has long eyelashes to keep sand out of eyes
- Has slit nostrils that can close
- Broad feet to reduce tendency to skin in sand
- Thick fur to insulate body against heat
- Stomach has a large water holding capacity
- Nasal passage is lined with mucus which absorbs water vapour during inhalation, so water is conserved.
- Hump contains fat for energy reserves.
What are the adaptive features of a Venus flytrap?
- Live where there is shortage of nitrates
- Leaves with tooth-like edges
- Sensitive hairs are triggered when an animal lands on, causing leaves to close on it
- Leaves secrete Protease to digest insect protein and produce amino acids.
What are the adaptive features of a bat?
- Body covered in fur for insulation.
- The fingers are long to increase S.A of the wing.
- Makes high pitched sounds, reflected back from prey.
What are the adaptive features of a Hare?
- Long ears pick up vibrations
- Fur gives insulation and camouflage
- Long hind legs for running and kicking
- Eyes on side of head give 180 vision
What are Hydrophytes?
These are plants that are adapted to grow and live in water such as ponds, lakes, rivers.
ex: Water lily
What are the Adaptive features of Hydrophytes?
- Wide, Flat leaves with large air spaces increase surface area, making them buoyant to float on water, efficiently absorbing more sunlight for photosynthesis.
- Have Small roots since they absorb water from stem and leaves
- Stomata are mostly present on upper epidermis to allow efficient gas exchange.
What are Xerophytes?
These are plants that are adapted to survive in dry environments with limited access to water.
- Their features allow them to maximize water uptake and minimize water loss.
ex: Cacti, Marram grass, Pine trees
What are the adaptive features of Xerophytes?
- Thick, waxy cuticle prevents water loss.
- Sunken stomata creates high humidity, reducing transpiration.
- Thick stems/leaves to store water which also have small S.A to reduce evaporation. (leaves can be needles)
- Extensive roots maximize water uptake.
What is the Natural Selection process?
Natural selection:
- First, genetic variation occurs in a population, producing many offspring.
- The offspring will grow and struggle for survival, including competition for resources.
- Individuals that are better adapted to the environment have greater chance of reproducing compared to others.
- These individuals then may pass the alleles responsible for better adaptation to the next generation.
- AS a result, this new variety replaces the original variety.
