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biology > variation and selection > Flashcards

variation and selection Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

define variation

A

differences between
individuals of the same species

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2
Q

define continuous variation

A
  • a range of phenotypes between two extremes; examples
    include body length and body mass
  • Data can take a range of values between two extremes
  • It is not categoric
  • Caused by both genes and the environment
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3
Q

define discontinuous variation

A
  • results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peas
  • Data can only take particular values with no intermediates
  • It is categoric
  • Caused by genes alone (not the environment)
  • e.g. blood groups are A, AB, B, O
  • e.g. seed shape and colour in peas, fur colour in animals
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4
Q

define gene mutation

A
  • change in base sequence of DNA
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5
Q

define mutation

A
  • genetic change
  • mutation is the way new alleles are formed
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6
Q

what increases rate/chances of mutation?

A
  • ionising radiation
  • and some chemicals
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7
Q

what are the sources of genetic variation in populations?

A
  • mutation
  • meiosis
  • random mating
  • random fertilisation
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8
Q

define adaptive features

A
  • inherited feature that helps an organism to
  • survive and reproduce in its environment
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9
Q

adaptive features of hydrophytes

A
  • leaves have large surface area ; to float
  • little / no roots ; roots for anchorage only / no need for roots to absorb water or mineral ions
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10
Q

adaptive features of xerophytes

A
  • roots branch many times ; have many roots hairs ; to give a large surface area (for absorption of water)
  • root cells have low water potential ; to absorb water by osmosis from salty soils
  • deep roots to absorb water from the water table
  • long and spread out below the surface ;to absorb water when it rains
  • sunken stomata ;
  • stomata close during the day and open at night
  • thick cuticle
  • few leaves
  • hair on leaves
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11
Q

Describe the process of natural selection

A

(a) genetic variation within populations
(b) production of many offspring
(c) struggle for survival, including competition
for resources
(d) a greater chance of reproduction by
individuals that are better adapted to the
environment than others
(e) these individuals pass on their alleles to the
next generation

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12
Q

define fitness

A

Probability of an organism surviving and reproducing in their environment

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13
Q

describe adaptation

A
  • the process, resulting from natural selection,
  • by which populations become more suited to their environment
  • over many generations
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14
Q

How may natural selection lead to development of antibiotic resistant bacteria?

A

Genetic variation means some bacteria have mutations for antibiotic resistance
- If antibiotic used, these bacteria better adapted to survive and duplicate
- Favourable alleles passed on to future bacteria
- Soon whole population of bacteria is resistant to the antibiotic

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15
Q

Describe selective breeding

A

(a) selection by humans of individuals with
desirable features
(b) crossing these individuals to produce the
next generation
(c) selection of offspring showing the desirable
features

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16
Q

Describe selective breeding in plants

A
  • Humans choose plants with desirable characteristics (e.g high yield, disease/pest resistance)
  • Cross pollinate selected plants
  • Plants that grow with desirable characteristics are chosen and crossed
  • Process repeats over many generations
17
Q

Describe selective breeding in domesticated animals

A
  • Humans choose individual animals with desirable characteristics (e.g more milk production,
    better quality fur)
  • Make them breed (or use artificial insemination)
  • Offspring with desirable characteristics are bred
  • Process repeats over many generations
18
Q

Outline the differences between natural and
artificial selection

A

Natural selection
* Individuals that survive and reproduce have characteristics that suit their environment.
* Long and slower process; speed is quite slow.
* Happens to all wild organisms.
* Individuals likely to be healthier bc they’re less likely to be inbred.
* New disease occurs/environmental change; chances of survival increased bc more variation in population.

Artifical selection
* Individuals that reproduce have characteristics that humans think are desirable.
* Speed of change is faster; quite large changes in features can happen in shorter periods of time.
* Happens to only organisms that humans choose.
* Involves breeding from closely related organisms; causes inbreeding. Variation in a population is reduced. Population may have genetic disorders.
* Chances of survival lower; less variation; not adaptive features; features breeder wants.

19
Q

What is the main energy source for biological systems?

A
  • Sun
20
Q

Describe the flow of energy through living
organisms

A
  • Light energy from sun transferred to chemical energy by plants
  • Energy flows through living organisms as one organism eats another
  • Eventually energy transferred to the environment
  • By excretion, decomposition, respiration.
21
Q

define food chain

A
  • shows transfer of energy
  • from 1 organism to next
  • beginning with a producer
22
Q

define food web

A
  • network of interconnected food chains
23
Q

define producer, herbivore, carnivore, consumer, decomposer

A

Producer
* organism that makes its own organic nutrients,
* usually using energy from sunlight,
* through photosynthesis

herbivore
* organism that get its energy by eating plants

carnivore
* organism gets its energy by eating other animals

consumer
* organism that gets its energy by feeding on other organisms
* may be classified as primary, secondary, tertiary, quaternary

decomposer
* organism that gets its energy from dead waste/organic material

24
Q

what’s a pyramid of numbers?

A
  • diagram representing no of organisms at each trophic level
  • in a given ecosystem at any one time.
25
Q

what’s pyramid of biomass?

A
  • diagram representing biomass
    (no. of individuals x their mass)
26
Q

advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain

A
  • in a pyramid of numbers 1 large individual is shown in the same way as one very tiny individual; so pyramid of biomass more accurate as organism’s size take into account.
  • pyramid of biomass is pyramid shaped whereas a pyramid of numbers is not always
  • biomass is an indicator of the energy available

disadvantage - data difficult to obtain as dry mass required

27
Q

advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain

A
  • allows comparsion of species of similar biomass but very diff lifespans
28
Q

Explain why the transfer of energy from one trophic level to another is often not efficient
Explain, in terms of energy loss, why food chains
usually have fewer than five trophic levels

A
  • little energy is transferred from one trophic level to the next
  • some parts of food e.g roots or bones arent eaten by organism so energy isnt taken in.
  • some parts of food indigestible (fibre) so pass through organisms and come out as faeces.
  • so much energy lost at each stage; not enough to support more organisms after 4-5 stages.
29
Q

Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants

A
  • Energy’s lost at each trophic level in a food chain
  • More efficient to eat plant
  • e.g eating cow fed on veggies, you would be higher up food chain then if u were eating veggies itself. less energy that was in veggies would reach u bc theres extra tophic lvl between u n plant
30
Q
  1. impact humans have through overharvesting of food species
  2. impact humans have through introducing foreign species to habitat
A
  • Over harvesting of food species deprives consumers of food
  • Consumers may switch to eating other foods
  • Introducing foreign species means more competition for food
  • Less food available for others
31
Q

What’s biomass
How is biomass measured?

A
  1. Total amount of living material in an organism.
    • Organism killed
      - Heated to remove water
      - Constant dry mass measured

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