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biodiversity Flashcards

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1
Q

define species and species richness

A
  1. Species = (A group of) organisms that are
    able to produce fertile offspring;
  2. Species richness = the number of (different)
    species in a community
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2
Q

What is the structure of DNA in eukaryotic cells?

A

Long, linear DNA associated with histone proteins

Eukaryotic DNA is found in the nucleus.

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3
Q

What is the structure of DNA in prokaryotic cells?

A

Short, circular DNA not associated with proteins

Prokaryotic DNA is found in the cytoplasm.

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4
Q

What are the similarities between eukaryotic and prokaryotic DNA?

A
  • Nucleotide structure is identical
  • Adjacent nucleotides joined by phosphodiester bonds
  • Complementary bases joined by hydrogen bonds
  • DNA in mitochondria/chloroplasts similar to prokaryotic DNA

Both types of DNA are composed of the same nucleotides (A, T, C, G).

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5
Q

What is a chromosome?

A

Long, linear DNA + its associated histone proteins in the nucleus of eukaryotic cells

Chromosomes are formed during cell division.

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6
Q

What is a gene?

A

A sequence of DNA bases that codes for the amino acid sequence of a polypeptide or a functional RNA

Functional RNA includes ribosomal RNA or tRNA.

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7
Q

What is a locus?

A

Fixed position a gene occupies on a particular DNA molecule

Each gene has a specific location on a chromosome.

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8
Q

Describe the nature of the genetic code.

A
  • Triplet code
  • Universal
  • Non-overlapping
  • Degenerate

The triplet code means that each sequence of three bases codes for one amino acid.

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9
Q

What are non-coding base sequences?

A

DNA that does not code for amino acid sequences, found between genes and within genes (introns)

Much of the nuclear DNA in eukaryotes does not code for polypeptides.

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10
Q

What is an exon?

A

Base sequence of a gene coding for amino acid sequences in a polypeptide

Exons are the coding regions that remain after splicing.

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11
Q

What is an intron?

A

Base sequence of a gene that doesn’t code for amino acids, found in eukaryotic cells

Introns are removed during RNA splicing.

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12
Q

Define ‘genome’.

A

The complete set of genes in a cell

Includes genes in mitochondria and/or chloroplasts.

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13
Q

Define ‘proteome’.

A

The full range of proteins that a cell can produce

Coded for by the cell’s DNA/genome.

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14
Q

What are the two stages of protein synthesis?

A
  • Transcription
  • Translation

Transcription occurs in the nucleus, while translation occurs at ribosomes.

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15
Q

Describe the structure of tRNA.

A

Folded into a clover leaf shape, has an anticodon and an amino acid binding site

tRNA is shorter and has hydrogen bonds between paired bases.

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16
Q

Describe the structure of mRNA.

A

Linear/straight, longer and variable length, contains codons

mRNA does not have hydrogen bonds between bases.

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17
Q

How is mRNA formed by transcription in eukaryotic cells?

A
  • Hydrogen bonds between DNA bases break
  • One DNA strand acts as a template
  • Free RNA nucleotides align
  • Uracil replaces thymine
  • RNA polymerase joins adjacent RNA nucleotides

Pre-mRNA is spliced to remove introns.

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18
Q

What is a gene mutation?

A

A change in the base sequence of DNA on chromosomes

Can arise spontaneously during DNA replication.

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19
Q

What is a mutagenic agent?

A

A factor that increases the rate of gene mutation, such as ultraviolet (UV) light

Other examples include certain chemicals and radiation.

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20
Q

Explain the effects of a substitution mutation.

A

Changes one triplet, which can change one mRNA codon and one amino acid in the polypeptide

May not change the amino acid due to the degenerate nature of the genetic code.

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21
Q

Explain the effects of a deletion mutation.

A

One nucleotide removed, causing a frameshift and changing the sequence of mRNA codons and amino acids

This can lead to a completely different protein.

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22
Q

What is genetic diversity?

A

The number of different alleles of genes in a population

Increased genetic diversity can enhance adaptability and survival.

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23
Q

Describe how meiosis leads to genetic variation.

A
  • Crossing over between homologous chromosomes
  • Independent segregation of homologous chromosomes

These processes create new combinations of alleles.

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24
Q

What is the difference between diploid and haploid cells?

A
  • Diploid: has 2 complete sets of chromosomes (2n)
  • Haploid: has a single set of unpaired chromosomes (n)

Diploid cells are typically somatic cells, while haploid cells are gametes.

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25
Q

Explain why the number of chromosomes is halved during meiosis.

A

Homologous chromosomes are separated during meiosis I

This reduction is essential for maintaining chromosome number across generations.

26
Q

How is the number of possible combinations of chromosomes in daughter cells calculated following meiosis?

A

2^n, where n = number of pairs of homologous chromosomes

n is half the diploid number.

27
Q

How does random fertilization increase genetic variation?

A

Creates new allele combinations from two gametes

This further increases the genetic diversity of the offspring.

28
Q

What are the outcomes of mitosis compared to meiosis?

A
  • Mitosis: 2 genetically identical daughter cells
  • Meiosis: 4 genetically varied daughter cells

Mitosis maintains chromosome number, while meiosis reduces it.

29
Q

What is the importance of meiosis?

A

Produces haploid gametes, restores diploid number at fertilization, and increases genetic variation

Essential for sexual reproduction.

30
Q

What results from the formation of a new, advantageous allele?

A

Change in polypeptide positively affects protein properties, resulting in a selective advantage

This leads to increased chances of survival and reproductive success.

31
Q

What is the outcome of the second meiotic division?

A

Halves the chromosome number

The first meiotic division separates homologous pairs, resulting in diploid to haploid transition.

32
Q

What does crossing over create?

A

New combinations of maternal and paternal alleles on chromosomes

This process contributes to genetic diversity.

33
Q

Define genetic diversity.

A

Number of different alleles of genes in a population

34
Q

What are alleles?

A

Variations of a particular gene at the same locus with different DNA base sequences

Alleles arise by mutation.

35
Q

How is a population defined?

A

A group of interbreeding individuals of the same species

36
Q

Explain the importance of genetic diversity.

A

Enables natural selection to occur

New alleles may benefit the organism in certain environments, increasing survival and reproductive success.

37
Q

What is evolution?

A

Change in allele frequency over many generations in a population through natural selection

38
Q

List the principles of natural selection.

A
  • Mutation
  • Advantage
  • Reproductive success
  • Inheritance
  • Allele frequency

These principles contribute to species adapting to their environment.

39
Q

Describe three types of adaptations.

A
  • Anatomical - structural features
  • Physiological - processes or chemical reactions
  • Behavioural - ways of acting

All adaptations increase the chance of survival.

40
Q

What is directional selection?

A

Selection favoring organisms with an extreme variation of a trait

Example: Antibiotic resistance in bacteria.

41
Q

What is stabilizing selection?

A

Selection favoring organisms with average trait variations

Example: Human birth weight.

42
Q

True or False: Antibiotics cause mutations.

A

False

Mutations occur randomly; antibiotics act as selection pressures.

43
Q

Describe aseptic techniques used in microbial growth investigations.

A
  • Wash hands
  • Sterilize equipment
  • Flame neck of bacterial bottles
  • Minimize petri dish opening

These techniques prevent contamination.

44
Q

What is the purpose of a control in experiments with antimicrobial agents?

A

Ensures that growth prevention is due to the antimicrobial and not other factors

Example: Paper disc with water.

45
Q

Explain the importance of maintaining a pure culture of bacteria.

A

Prevents outcompeting or harmful bacteria affecting results

46
Q

Define species.

A

A group of organisms that can interbreed to produce fertile offspring.

47
Q

Why are two different species unable to produce fertile offspring?

A

Different chromosome numbers prevent homologous pairs from forming

This leads to issues during meiosis.

48
Q

What is a phylogenetic classification system?

A

Arrangement of species into taxa based on evolutionary origins and relationships

49
Q

Name the taxa in the hierarchy of classification.

A
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

This hierarchy is arranged from largest to smallest group.

50
Q

What is the binomial naming system?

A

A two-part name consisting of genus and species

51
Q

What does a branch point in a phylogenetic tree represent?

A

A common ancestor

52
Q

What advances have clarified evolutionary relationships?

A
  • Genome sequencing
  • Advances in immunology

These methods allow comparison of DNA and protein structures.

53
Q

Define biodiversity.

A

Variety of living organisms, including species, genetic, and ecosystem diversity

54
Q

What is species richness?

A

A measure of the number of different species in a community

55
Q

What does the index of diversity describe?

A

The relationship between species richness and population size of each species

56
Q

Explain why index of diversity is more useful than species richness.

A

It accounts for the number of individuals in each species, providing a more complete picture

57
Q

What is the formula for index of diversity?

A

d = N(N - 1) / Σ n(n - 1)

Where N is the total number of organisms and n is the total number of organisms of each species.

58
Q

How can farming techniques reduce biodiversity?

A
  • Removal of woodland
  • Monoculture
  • Use of herbicides and pesticides

These practices reduce habitat variety and food sources.

59
Q

What is the balance between conservation and farming?

A

Conservation increases biodiversity but may lower yields, affecting farmer profits

60
Q

How can biodiversity be increased in agriculture?

A
  • Reintroduction of field margins
  • Reducing pesticide use
  • Intercropping
  • Crop rotation

These methods promote a variety of species.

61
Q

How can genetic diversity be measured?

A
  • Comparing observable characteristics
  • Comparing DNA sequences
  • Comparing mRNA sequences
  • Comparing amino acid sequences

Each method helps indicate relationships between organisms.

62
Q

What are key considerations in quantitative investigations of variation?

A
  • Collect data from random samples
  • Use a large sample size
  • Ensure ethical sampling
  • Calculate mean and standard deviation
  • Use appropriate statistical tests

These steps ensure reliable results.

Bio Aqa (7 decks)

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