Classification and Evolution Flashcards
What is classification in biology?
The process of sorting living organisms into groups based on shared characteristics.
What are the seven taxonomic ranks in classification?
(Linnaen classification)
Kingdom, Phylum, Class, Order, Family, Genus, Species.
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Why do scientists classify organisms?
- To identify species easily.
- To predict characteristics of organisms.
- To find evolutionary links between species.
What is hierarchical classification?
A system where large groups are divided into smaller, more specific groups at each level.
What are the three domains of life?
Archaea, Bacteria, and Eukarya.
What is a species?
A group of organisms that can reproduce and produce fertile offspring.
Why are mules and hinnies infertile?
Because they have an odd number of chromosomes, preventing proper meiosis.
What is binomial naming?
A system of naming species using two Latin words: Genus (capitalized) and species (lowercase).
How should scientific names be written?
In italics when typed or underlined when handwritten, with the Genus capitalised and species in lowercase.
What is the scientific classification of humans?
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: sapiens
Why do some organisms have similar names in binomial nomenclature?
If they share a genus, they are closely related, like Canis lupus (wolf) and Canis familiaris (dog)
What are the five kingdoms of classification?
Prokaryotae, Protoctista, Fungi, Plantae, Animalia
What distinguishes prokaryotes from eukaryotes?
Prokaryotes lack a nucleus and membrane-bound organelles, while eukaryotes have both.
What are the key features of Prokaryotae?
Unicellular
No nucleus or membrane-bound organelles
DNA is naked (not in a nucleus)
Absorb nutrients via diffusion or photosynthesis
What are the key features of Protoctista?
Mostly unicellular
Nucleus and membrane-bound organelles
Some have chloroplasts
Can be autotrophic or heterotrophic
What are the key features of Fungi?
Can be unicellular or multicellular
Nucleus and membrane-bound organelles
Cell wall made of chitin
No chloroplasts
Absorb nutrients (saprophytic feeding)
What are the key features of Plantae? (e.g. roses, grass)
Multicellular
Cell walls made of cellulose
Contain chlorophyll
Photosynthetic (autotrophic)
What are the key features of Animalia?
(e.g. mammals, reptiles)
Multicellular
No cell wall
Heterotrophic
Move using cilia, flagella, or contractile proteins
Why has classification changed over time?
Due to advances in DNA analysis and molecular studies, showing evolutionary relationships more accurately.
What is the three-domain system?
Organisms are classified into:
Bacteria (true bacteria)
Archaea (ancient bacteria)
Eukarya (organisms with nuclei)
How do Archaea differ from Bacteria?
Their RNA polymerase and cell wall structure are different, and they live in extreme environments.
What is phylogeny?
The study of evolutionary relationships between organisms, showing how closely related they are.
What is a phylogenetic tree?
A diagram that represents evolutionary relationships between organisms, showing their common ancestors.
How do you interpret a phylogenetic tree?
Tips = species/groups
Branch points (nodes) = common ancestors
Closer common ancestor = more closely related
How are phylogenetic trees created?
By comparing species’ physical traits, genetic makeup, and fossil evidence.
How does phylogenetic classification differ from Linnaean classification?
Linnaean classification groups organisms, while phylogeny shows their evolutionary history.
What are the advantages of phylogenetic classification?
Continuous classification (not forced groups)
More accurate evolutionary relationships
Shows links between species
Why is phylogenetic classification more accurate?
It avoids misclassifications—e.g., dolphins look like fish but are mammals based on evolutionary history.
What does a closer common ancestor mean?
The more recent the ancestor, the more closely related the species are.
Why are some species lower in a phylogenetic tree?
They evolved earlier in history.
How do phylogenetic trees show evolutionary relationships?
They visually map species’ descent from common ancestors, showing who is more closely related.
Who was Charles Darwin and what did he propose?
A scientist in the 1800s who developed the theory of evolution by natural selection, based on observations from the HMS Beagle expedition.
What evidence suggested the Earth was older than previously thought?
Geologists observed slow processes like erosion, and paleontologists found fossils of extinct organisms, indicating Earth is millions of years old.
What did Darwin observe about finches on the Galapagos Islands?
Different species had different beak shapes suited to their food sources, demonstrating natural selection.
Who was Alfred Russell Wallace?
A scientist who independently developed a similar theory of evolution while studying species in Southeast Asia.
How do fossils support evolution?
Older rock layers contain simpler organisms, while newer layers contain more complex ones, showing gradual evolution. However, the fossil record is incomplete due to preservation challenges.
What is comparative anatomy and what are homologous structures?
Comparative anatomy studies structural similarities in different species. Homologous structures are body parts that have a similar internal structure but may serve different functions, indicating they evolved from a common ancestor. An example is the pentadactyl limb found in vertebrates, which has adapted for swimming in whales, flying in bats, and grasping in humans.
What is comparative biochemistry and how does cytochrome C support evolution?
Comparative biochemistry examines molecular similarities between species. Cytochrome C, a protein involved in respiration, has conserved amino acid sequences, with closely related species having more similar sequences, indicating common ancestry.
How does DNA analysis support evolution?
Similarities in DNA and ribosomal RNA sequences indicate evolutionary relationships, such as humans and chimpanzees sharing a recent common ancestor.
What is variation, and what are its two types?
Variation is the difference in characteristics between organisms. It can be interspecific variation (differences between species) or intraspecific variation (differences within a species).
Give examples of interspecific and intraspecific variation.
Interspecific: A mouse has four legs and fur, whereas a bird has wings and feathers.
Intraspecific: People vary in height, eye colour, and intelligence.
What are the main causes of variation?
Genetic variation (differences in DNA inherited from parents) and environmental variation (differences caused by surroundings).
What is genetic variation? Give an example.
Genetic variation is inherited differences in DNA. Example: Eye colour differences in humans.
What is environmental variation? Give an example.
Environmental variation is caused by surroundings. Example: A plant growing taller due to better sunlight.
What are the genetic causes of variation?
Genetic variation arises due to differences in genes and alleles within a population. Causes include alleles, mutations, meiosis, sexual reproduction, and chance.
How do alleles contribute to genetic variation?
Alleles are different versions of the same gene. Individuals inherit different combinations of alleles, leading to variation in traits like blood type (A, B, O).
How do mutations cause variation?
Mutations are changes in DNA that can alter proteins and traits. Mutations in body cells affect only the individual, while mutations in gametes can be inherited.
How does meiosis create genetic variation?
Meiosis involves independent assortment and crossing over, which mix genetic material and create unique combinations in gametes.
How does sexual reproduction contribute to variation?
Offspring inherit a combination of traits from both parents, leading to unique genetic characteristics.
What role does chance play in genetic variation?
The random fusion of gametes during fertilisation results in new allele combinations, increasing variation.
What is environmental variation?
Differences caused by environmental factors, such as a plant growing larger due to more sunlight. Environmental traits like scars are not inherited.
Give an example of environmental variation in plants.
Two rose bushes in different positions in a garden grow differently—one in more sunlight grows taller than one in the shade.
How do environmental and genetic factors interact in variation?
Some traits, like height and skin colour, are influenced by both genetics and environment. For example, skin colour is inherited but darkens with sun exposure.
Why is it difficult to separate genetic and environmental influences on variation?
Many traits, such as intelligence, involve both genetic and environmental factors, making it hard to determine the exact cause.
What are the two types of variation in characteristics?
Discontinuous variation- A characteristic that can only exist in certain values with no in-between states, often determined by genetic factors.
e.g. An animal’s sex (male or female) or blood type
Continuous variation- A characteristic that can take any value within a range, forming a continuum e.g. Height and body mass.
How is discontinuous and continuous variation usually represented?
discontinuous- By a bar chart.
continuous- In a frequency table and then plotted as a histogram.
What influences characteristics that show continuous variation?
Multiple genes (polygenic inheritance) and environmental factors.
What shape do normal distribution curves typically form?
A bell-shaped curve, with symmetrical distribution where:
The mean, mode, and median are the same.
50% of values are below and 50% above the mean.
Most values are near the mean, with fewer at the extremes.
What percentages of data fall within 1, 2, and 3 standard deviations in a normal distribution?
68% within 1 standard deviation.
95% within 2 standard deviations.
99.7% within 3 standard deviations.
What is standard deviation, and what does it indicate?
Standard deviation (σ) measures data spread:
High σ = Large variation.
Low σ = Data is closely clustered around the mean.
How is standard deviation calculated?
SD= (x - mean of x)^2/ n-1
What is Student’s t-test used for?
To compare the mean values of two data sets and determine if the difference is statistically significant.
What are the key requirements for using a t-test?
Data must be normally distributed.
Enough data should be collected for reliability.
Different sample sizes may be tested.
What does a significance level of 0.05 mean in hypothesis testing?
There is a 5% chance of rejecting a true null hypothesis
How do you interpret a t-test result?
If the calculated t-value is greater than the critical value, the difference is statistically significant.
If the p-value is ≤ 0.05, we reject the null hypothesis.
If p ≤ 0.01, the result is highly significant.
What other statistical test can be used in data analysis?
The correlation coefficient measures the relationship between two sets of data.
It is used to see if two sets of ranked data are correlated.
If the coefficient is +1, there is a perfect positive correlation.
If it is -1, there is a perfect negative correlation.
A coefficient of 0 means there is no correlation.
What are the different types of correlation shown in graphs?
Positive correlation: As one set of data increases, the other increases too.
Negative correlation: As one set of data increases, the other decreases.
No correlation: No clear relationship between the two data sets.
what is the formula for spearman’s rank?
1- (sum of 6 x D^2/ n^3-n)
What steps are followed to calculate Spearman’s Rank in the example?
Rank both data sets from lowest to highest.
If values are identical, assign the average rank.
Find the difference in ranks for each pair.
Square each difference and sum them
Substitute values into the formula
How do you determine if a correlation is statistically significant?
Use the Student’s t-test formula
Compare t-value to the critical value in significance tables.
If 𝑝<0.05, the result is significant (less than 5% probability of occurring by chance).
If p>0.05, the result is not significant (more than 5% probability of occurring by chance).
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