topic 4C: diversity and classification Flashcards
What is a species?
A group of organisms that can (interbreed to) produce FERTILE OFFSPRING
Suggest why 2 different species are unable to produce fertile offspring
● Different species have DIFFERENT CHROMOSOME NUMBERS → offspring may have ODD CHROMOSOME NUMBER
● So HOMOLOGOUS PAIRS cannot form → MEIOSIS cannot occur to produce gametes
Explain why courtship behaviour is a necessary precursor to successful mating
● Allows RECOGNITION of members of SAME SPECIES → so FERTILE OFFSPRING produced
● Allows recognition / attraction of OPPOSITE SEX
● Stimulates and SYNCHRONISES MATING and production and release of gametes
● Indicates SEXUAL MATURITY and fertility
● Establishes a PAIR BOND to raise young
Describe a phylogenetic classification system
● Species (attempted to be) arranged into GROUPS, called TAXA, based
on their EVOLUTIONARY ORIGINS (common ancestors) and RELATIONSHIPS
● Uses a HIERARCHY:
○ SMALLER GROUPS are placed within larger groups
○ NO OVERLAP between groups
Name the taxa in the hierarchy of classification
- Domain (largest / broadest)
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species (smallest)
How is each species universally identified?
A BINOMIAL consisting of the name of its GENUS and SPECIES, eg. Homo sapiens
Suggest an advantage of binomial naming
UNIVERSAL so no CONFUSION as many organisms have more than one common name
How can phylogenetic trees be interpreted?
● Branch point = COMMON ANCESTOR
● Branch = EVOLUTIONARY path
● If two species have a more recent common
ancestor, they are MORE CLOSELY RELATED (eg. C & D)
Describe two advances that have helped to clarify evolutionary relationships between organisms
- Advances in GENOME SEQUENCING → allowing comparison of DNA BASE SEQUENCES
● More DIFFERENCES in DNA base sequences → MOST DISTANTLY RELATED AND EARLIER COMMON ANCESTOR
● As MUTATIONS (change in DNA base sequences) BUILD UP OVER TIME - Advances in immunology → allowing comparison of protein tertiary structure (eg.albumin)
● HIGHER AMOUNT of protein from one species BINDS TO ANTIBODY against
the same protein from another species → MORE CLOSELY RELATED AND MORE RECENT COMMON ANCESTOR
● As indicates a similar AMINO ACID SEQUENCE and TERTIARY STRUCTURE
● So less time for MUTATIONS to build up
What is biodiversity?
● VARIETY of living organisms (species, genetic and ecosystem diversity)
● Can relate to a range of HABITATS, from a small LOCAL habitat to the EARTH
What is a community?
All POPULATIONS of different species that live in an area
What is species richness?
A measure of the NUMBER of DIFFERENT SPECIES in A COMMUNITY
What does an index of diversity do?
Describes the RELATIONSHIP between:
1. The NUMBER OF SPECIES in a community (species richness)
2. The number of INDIVIDUALS IN EACH SPECIES (population size)
Suggest why index of diversity is more useful than species richness
● Also takes into account NUMBER OF INDIVIDUALS IN EACH SPECIES
● So takes into account that some species may be present in SMALL or HIGH NUMBERS
What is the formula for index of diversity?
d = N (N - 1) / Σ n (n -1)
N = total number of organisms of ALL SPECIES
n = total number of organisms of EACH SPECIES, Σ = the sum of
List the steps involved in calculating an index of diversity
- Calculate the total number of organisms (N), if not given
- Multiply N by (N - 1)
- For each species, multiply the number of organisms (n) by (n - 1)
- Add up all the values of n(n - 1) to get Σn(n-1)
- Divide N(N - 1) by Σn(n - 1)
Describe how index of diversity values can be interpreted
● High → MANY SPECIES present (high species richness) and species EVENLY REPRESENTED
● Low → habitat DOMINATED by one / a few species
Explain how some farming techniques reduce biodiversity
Removal of WOODLAND AND HEDGEROWS, MONOCULTURE (growing one type of crop) and
Use of HERBICIDES to KILL WEEDS :
● Reduces VARIETY OF PLANT SPECIES
● So fewer HABITATS and niches
● And less VARIETY OF FOOD SOURCES
Use of PESTICIDES to kill pests: PREDATOR population of pest decreasesExplain the balance between conservation and farming
Explain the balance between conservation and farming
● Conservation required to INCREASE BIODIVERSITY
● But when implemented on farms, YIELDS can be reduced, reducing PROFIT AND INCOME for farmers
○ Eg. by reducing land area for crop growth, increasing competition, increasing pest population
● To offset loss, FINANCIAL INCENTIVES AND GRANTS are offered
Give examples of how biodiversity can be increased in areas of agriculture
● Reintroduction of FIELD MARGINS and HEDGEROWS (where farmers only grow one type of crop)
● Reduce use of PESTICIDES
● Growing DIFFERENT CROPS in the same area (intercropping)
● Using CROP ROTATION of nitrogen fixing crops instead of fertilisers
How can genetic diversity within or between species be measured?
● Comparing FREQUENCY OF MEASURABLE OR OBSERVABLE CHARACTERISTICS
● Comparing BASE SEQUENCE OF DNA
● Comparing BASE SEQUENCE OF mRNA
● Comparing AMINO ACID SEQUENCE of a specific PROTEIN encoded by DNA and mRNA
Explain how comparing DNA, mRNA and amino acid sequences can indicate
relationships between organisms within a species and between species
● More DIFFERENCES in sequences → MORE DISTANTLY RELATED and EARLIER COMMON ANCESTOR
● As MUTATIONS (change in DNA base sequences) BUILD UP OVER TIME
● More mutations cause more changes in AMINO ACID SEQUENCES
Explain the change in methods of investigating genetic diversity over time
● Early estimates made by inferring DNA differences from MEASURABLE OR OBSERVABLE CHARACTERISTICS
○ Many CODED FOR BY MORE THAN ONE GENE → difficult to distinguish one from another
○ Many influenced by ENVIRONMENT → differences due to environment not genes
● Gene technologies allowed this to be replaced by direct investigation of DNA SEQUENCES
Explain how data should be collected when investigating variation within a
species quantitatively
● Collect data from RANDOM SAMPLES → to REMOVE BIAS
○ Use a GRID and divide area into squares
○ Use a RANDOM NUMBER GENERATOR to obtain random COORDINATES
● Use SAME METHOD OF MEASUREMENT each time
● Use a LARGE SAMPLE SIZE and measure a LARGE NUMBER of organisms → so REPRESENTATIVE of population
● Calculate a RUNNING MEAN and sample until number becomes (fairly) CONSTANT
● (Where applicable) ensure sampling is ETHICAL → must NOT HARM organism and must allow release UNCHANGED
