TOPIC 4: Biodiversity Flashcards
What is a species?
a group of closely related organisms with similar morphology, physiology and behaviour, which can interbreed to produce fertile, viable offspring.
What problems are there with defining species?
asexual, extinct, rare, geographically isolated
Define niche
the way an organism uses its environment & it’s role in the environment/ecosystem (predator? prey?)
What happens when two species occupy the same niche?
two species cannot occupy the same niche so there’s either splitting of the niche (one adapts to other niches) or extinction of one of the species.
What is fundamental niche?
the largest niche an organism could occupy without competition
What is realised niche?
the niche actually occupied due to competition
Define ecosystem
A self-sustaining life-supporting environment with biotic and abiotic factors
Define community
All the populations of different species sharing an ecosystem
Define population
total number of individual species within a community
What is an adaptation?
behavioural, physiological & anatomical features of an organism that help it survive in its habitat
What’s a physiological adaptation?
features of cells, tissues & systems to help an organism survive in its habitat
What’s a behavioural adaptation?
actions by organisms that help an organism survive in its habitat
What’s an anatomical adaptation?
visible, physical features that help an organism survive in its habitat
What’s co-adaptation?
adaptation of 2 or more organisms resulting in mutual benefit
What is directional selection?
selection pressure favoring one extreme trait, against the other
What is stabilising selection?
favoring mean, selecting against both extremes
What is disruptive selection?
favours both extremes, against mean
bimodal distribution
What causes allele frequencies to change?
genetic drift, non-random mating, natural selection, migration/emigration, mutations
What is genetic drift?
change in allele frequency due to chance (bottleneck - natural disaster/disease)
How does speciation happen?
- some individuals migrate to nearby islands & are geographically isolated;
different mutations and selection pressures; - species adapt to each region for survival & breeding;
- change in allele frequencies over time & difference between gene pools;
REPRODUCTIVE ISOLATION due to restricted gene flow
What is meant by populations adapting?
change in allele frequency in population
What factors increase the ability of a population to adapt?
strong selection pressure,
fast reproductive rate,
large gene pool
Why is it unlikely a population can be perfectly adapted to their environment?
environments change; time lag to adapt,
selection pressure is always present,
mutations (new alleles)
Why might it be a problem to be perfectly adapted?
dependence on other species makes them vulnerable if they die out,
less likely to survive environmental changes
Define biodiversity
the number of different species and genetic variation between them
What are endemics?
species unique to one geographic area
What is species richness?
number of different species in a given habitat
What is species evenness?
when species have similar abundances, no dominant species
Where are biodiversity hotspots usually located?
equatorial,
islands - reproductive isolation,
coastal - immigration
How is genetic variation measured?
- DNA sequenced to determine bases and alleles
- DNA copied using PCR and cut with restriction enzymes
- fragments separated by gel electrophoresis to create a banding pattern
What does 2 bands in gel electrophoresis mean?
heterozygous as there’s a band for each allele
What is the heterozygosity index?
number of heterozygotes / number of individuals in a population
Why is a large heterozygosity index good?
more heterozygous a population, the larger the gene pool;
increased chance of survival
Why is inbreeding bad?
heterozygosity lost, smaller gene pool;
decreased chance of survival;
recessive alleles have harmful effects (inbreeding depression)
What’s the order of taxonomic heirarchy?
kingdom, phylum, class, order, family, genus, species
What did Carl Woese discover?
new group of bacteria (methanogens) through RNA sequencing. They had no peptidoglycans in cell wall and membrane lipids differ from eukaryotes and bacteria.
proposed a new taxonomic structure (domains) - bacteria, eukaryota & archaea
What is meant by molecular phylogeny?
molecular differences in DNA & proteins showing evolutionary relationships between organisms.
organisms with similar characteristics are placed in the same group.
How is data critically evaluated by the scientific community?
- findings publish in a journal/presented at a scientific conference
- peer review to add weight to study
- other scientists repeat experiments to see if the findings can be replicated
What are the main threats to species survival?
poaching;
habitat loss;
alien species introduced;
pollution
What are the aims of captive breeding programmes?
increase no. of individuals of species;
maintain genetic diversity;
reintroduce into wild if possible
What are studbooks?
breeding records of captives which allow planning of programme to retain alleles and genetic diversity
How are seeds collected and conserved in a seedbank?
- viability checked with X-ray
- seeds surface sterilised & dried:
stored at low temp to prevent germination - germinating ability checked regularly - if below 75%, new seeds are collected
What are the advantages of conserving seeds of different sizes?
maintain genetic diversity;
more chance of having beneficial alleles, increasing chance of future survival:
less chance of all of them being susceptible to disease
Why are seeds conserved?
prevent species from becoming extinct;
conserves seeds with medicinal properties;
safeguarding useful genes;
allow for reintroduction of species in the future
Suggest an explanation for variation in characteristics in species
mutations;
large gene pool;
polygenic inheritance
How is change in phenotype brought about by natural selection?
- genetic variation w/in population due to mutations
- selection pressure - selection for better phenotype;
individuals with worse phenotype selected against & die out - individuals with advantageous alleles survive & breed, passing on the alleles to offspring
- over generations, there’s an increased frequency of the advantageous alleles/phenotype
How does geographic isolation affect genetic diversity of each individual population?
genetic diversity decreases;
closely related individuals inbreed;
risk of inbreeding depression - more chance of homozygous recessive genotypes;
genetic drift (loss of alleles)
How does transferring individuals from one population to another help endangered species survive?
increases gene pool;
increases potential for survival by better disease resistance/better physical characteristics for hunting
Why are offspring of different species infertile?
genetic incompatibility due to different number of chromosomes
Why don’t different species interbreed?
reproductive isolation;
don’t recognise courtship behaviour;
different breeding times;
physically incompatible (genitalia)
