Lec 3 slides and reading Flashcards
theory of evolution
accounts for the diversity of life, and explains similarities between different species
Similarities between different groups of species
-Systems of biological classifications have been based on easily visible structural characteristics
-Species are essentially groups of similar individuals capable of interbreeding with each other
-Similar species are grouped in the same genus
-Another set of facts that strongly support the theory of evolution is provided by modifications of the same structure in different species
-E.g. bones of bats and birds wings indicate they are modified forelimbs; flippers of whales and fish fins, both well adapted for swimming
Embryonic development
-Provides many examples of similarity between different groups of organisms, clearly suggesting descent from common ancestors
-Embryonic forms of different species are similar, even when the adults are different
-E.g. at one stage in mammalian development, structures appear that look like the developing gill slits of fish embryos → makes sense if we descended from fish-like ancestors
Since it’s the adult structures that adapt the organism to its environ, they usually get modified by selection
Vestigial organs
remnants of structures that were functional in the ancestors of present day organisms
E.g. human appendix → reduced version of part of the digestive tract that’s bigger in orangutans
E.g. fossils of snakes have been found with hindlegs, showing snakes evolved from lizard-like ancestors
Similarities in cells
-Basic feature of all animal, plant and fungal life is that their tissues are made up of cells
-Cells→ basis of bodies of all organisms other than viruses
In eukaryotes (all cellular non-bacterial life) the cells are organized into cytoplasm and nucleus within it that contains genetic material
Cytoplasm → contains complex set of tiny pieces of machinery with many subcellular structures
Mitochondria → generate cell’s energy
Chloroplasts → photosynthesis in green plants’ cells occurs
It’s now known that both of these are descended from bacteria that colonized cells and became integrated into them as essential components
prokaryotes
bacteria that are cells but simpler with no nucleus or organelles
viruses
viruses are the only non-cellular forms of life and are parasites that reproduce inside the cells of other organisms, and consist of a protein coat surrounding genetic material
proteins
Proteins are enzymes that take a chemical and carry out a procedure for it (like chemical scissors)
-Also have storage or transport functions (haemoglobin in RBCs transports oxygen)
-Structural proteins (keratin) forms skin, hair and nails
-Communication proteins (hormones, signal to control cell behaviour during development)
effect of mutations in the myosin protein gene
deafness
how are enzymes categorized
Enzymes categorized by the jobs they perform (digestive enzymes snip molecules into pieces)
process by which cells generate energy from food sources
In process by which energy generated by cells from food sources, there’s an energy source (sugar or fats) and goes thru chemical steps, some release energy
Metabolic pathway organized like an assembly line and enzymes carry out the different steps
Cells have pathways to make chemicals and to generate energy from foods
what does the functioning of each chemical pathway depend on
Functioning of each biochemical pathway depends on enzymes
If any enzyme in pathway stops working → end product will not be produced
E.g. albino mutations result from lack of an enzyme necessary for production of pigment melanin
what is stopping a pathway useful for
Stopping a step in a pathway is useful to control the output of cell machinery (cells contain inhibitors to carry out control functions - e.g. control of melanin production)
dna structure
Sugar phosphate backbone (structure of DNA- sugars connected to nucleotides)
Nucleotides: adenine, guanine, cytosine and thymine: A&T, G&C
When DNA replicates during cell division, the 2 strands unwind and a complementary daughter strand is combined from each parent strand
genes
Inheritance is the control of individuals’ characteristics by physical entities called genes (Gregor Mendel)
The genes that control the production of metabolic enzymes and other proteins(and thus determine individuals’ characteristics) are stretches of DNA carried in the chromosomes of each cell
Discovery that chromosomes carry genes in a linear arrangement was made in the fruitfly (Drosophila melanogaster)
true or false: order of genes on a chromosome can be rearranged during evolution
true
Chromosome is a long DNA molecule encoding hundreds of genes DNA of a chromosome is combined with protein molecules that help package it in neat coils inside the cells nucleus
Each gene encodes a different protein
Chromosomes carry the info needed to specify the amino acid sequences of an organism’s proteins, together with the controlling DNA sequences that determine which proteins will be produced by organism’s cells
What is a gene, and how does it determine the structure of a protein?
Gene is sequence of four chemical letters of the genetic code, in which sets of 3 adjacent letters (codons) correspond to each AA in the the protein for which the gene is responsible
Gene sequence is translated into the sequence of a protein chain (has triplets marking the end of the AA chain)
Change in sequence of a gene causes mutation (some mutation don’t change the protein sequence)
Across living organisms, the genetic code differs slightly, suggesting that all life on Earth has a common ancestor
In order to produce its protein product, DNA…
DNA sequence of a gene is first copied into a ‘message’ made of RNA, whose sequence of letters is copied from the gene by a copying enzyme
RNA message interacts with proteins and other RNA molecules, to translate the message and produce the protein specified by the gene (occurs in all cells - in eukaryotes occurs in cytoplasm & message has to move outside of nucleus first)
non coding DNA
In between genes on chromosomes are stretches of DNA that don’t code for proteins
Non-coding DNA acts as binding proteins that turn production of RNA messages of genes on or off as needed
E.g genes for hemoglobin are turned on in cells developing into RBCs but off in brain cells
cell division
Single-celled organisms(amoeba or yeast) can reproduce by division into 2 daughter cells
Fertilized egg of a multicellular organism, produced by fusion of egg and sperm, divides into 2 daughter cells as well
Genes are turned on and off to ensure that the right kind of cell is produced in the right place at the right time
When a cell divides, the DNA of the chromosomes is first replicated, so that there are 2 copies of each chromosome
-Cell division is a process with tight controls to ensure that the newly copied DNA sequence undergoes ‘proof-reading’ for errors
proof reading in RNA
Proof-reading that occurs in DNA replication does not happen when RNA is copied → viruses have high mutation rates and can evolve rapidly in host’s body
mutations and their effects
If a mutation results in a change in the amino acid sequence of a protein, the protein may malfunction (not fold up correctly/unable to do its job)
If it’s an enzyme→causes metabolic pathway to run slowly or not at all
In structural or communication proteins→ impairs cell functions or organism’s development
Many diseases in humans are caused by mutations
E.g mutations in genes involved in controlling cell division →cause cancer
Can lower survival or fertility of affected individuals
Gene sequence that leads to non-functional enzyme…
will be under-represented in next gen and will eventually be eliminated from population
Mutations causing loss of function…
can contribute to evolution when selection no longer acts to eliminate them
______ is the essential raw material on which NS acts to produce evolutionary changes
Genetic variability
sources of evidence for evolution
geology, homology, biogeography, domestication
endemism
things found somewhere that aren’t found anywhere else
endemism in Australia
isolated land mass has species there that aren’t found anywhere else with unique adaptations
convergent evolution
two organisms look or behave in a very similar way, even though they’re only distantly related.
This means they’ve independently evolved those similarities rather than inheriting them from a common ancestor. ‘
how many different lines of evidence can we make sense of only by invoking evolution
Fossil Record: Fossils show a timeline of life on Earth and reveal the progression of species through transitional forms, such as fossils of early hominids that show the gradual evolution of humans from apelike ancestors.
Comparative Anatomy: The study of similarities and differences in the anatomy of different species. Homologous structures (e.g., the limb bones of humans, birds, and whales) indicate a common ancestor, while analogous structures (e.g., wings of bats and insects) result from convergent evolution.
Biogeography: The distribution of species around the world makes sense in the context of evolution. For example, species on islands often resemble those on nearby continents, reflecting shared ancestry, while isolated ecosystems develop unique species.
Molecular Biology: DNA sequence comparisons across species show clear patterns of relatedness, with more closely related species sharing more genetic similarities. This molecular evidence aligns with evolutionary theory and allows scientists to trace common ancestry.
Embryology: The study of embryos reveals that many organisms go through similar stages of development, even when their adult forms are quite different. This suggests that they share a common developmental pathway inherited from a distant ancestor.
Direct Observation of Evolutionary Changes: We can observe evolution in action, such as the development of antibiotic resistance in bacteria or changes in the size of beaks in finches on the Galápagos Islands in response to environmental pressures.
Vestigial Structures: These are remnants of structures that served important functions in ancestors but are now reduced or functionless in modern species. Examples include the human appendix or whale pelvic bones.
Genomic Evidence: Genome-wide studies show patterns of genetic variation that can only be explained by descent with modification. Gene duplications, mutations, and non-functional “junk” DNA provide evidence of evolutionary processes over time.
how does new evidence about genetics and DNA evidence connect to Darwin
New Evidence: Darwin didn’t know about DNA, genes, or how traits were inherited, which left a gap in his understanding of the mechanism of evolution. With the discovery of DNA and the development of genetics, scientists found that traits are passed from generation to generation through genes, and random mutations in DNA can introduce new traits into a population.
How It Fits: Genetics provides the mechanistic basis for Darwin’s theory of evolution. Mutation creates genetic variation, which natural selection can act upon. The concept of heredity that Darwin speculated on is now fully explained through our understanding of genes.
No Inconsistencies: Genetics reinforces Darwin’s ideas by showing how traits are inherited and how new variations arise, perfectly fitting the theory of natural selection.
how does new evidence about molecular biology connect to darwin
New Evidence: DNA sequencing has allowed scientists to compare the genetic makeup of different species. This has led to the discovery of homologous genes (genes shared between species) and molecular clocks (the rate at which mutations accumulate), which provide precise data on the evolutionary relationships and the timing of divergence between species.
How It Fits: Molecular biology has allowed for greater precision in mapping evolutionary lineages and divergence times. The genetic similarities between species (such as humans and chimpanzees) confirm common ancestry, which Darwin proposed based on anatomical similarities.
No Inconsistencies: The genetic evidence aligns closely with Darwin’s concept of common descent, supporting the evolutionary tree he envisioned.
how does new evidence about the molecular clock connect to darwin
New Evidence: By measuring the rate at which mutations accumulate in DNA, scientists can estimate the time when two species last shared a common ancestor. This concept, called the molecular clock, wasn’t available in Darwin’s time.
How It Fits: The molecular clock has allowed scientists to date evolutionary events more precisely, offering a timeline that complements fossil evidence.
No Inconsistencies: Molecular clocks provide a timeline that aligns well with the fossil record, confirming the ages of divergence Darwin could only estimate roughly.
how does new evidence from the fossil record connect to darwin
New Evidence: Since Darwin’s time, many new transitional fossils have been discovered (e.g., Tiktaalik as a transitional form between fish and amphibians, or feathered dinosaurs that bridge the gap between reptiles and birds).
How It Fits: These fossils provide concrete evidence of the gradual changes Darwin proposed. Transitional forms show how one species evolved into another, illustrating the gradual process of evolution.
No Inconsistencies: The new fossil discoveries provide physical evidence of the “missing links” Darwin predicted, further validating his theory.
how does new evidence of genomics and comparative genomics connect to darwin
New Evidence: Whole-genome comparisons across species have revealed deep genetic relationships, with even distantly related organisms sharing significant portions of their DNA. The study of non-coding DNA and shared endogenous retroviruses (ERVs) also provide evidence of common ancestry.
How It Fits: Genomics has provided fine-scale data on how closely related species are and has uncovered patterns of evolutionary history encoded in the genome itself. This allows us to trace ancestry and evolutionary events with great precision.
No Inconsistencies: Genomic evidence consistently supports Darwin’s tree of life and deepens our understanding of the genetic relationships between species.
how does new evidence of developmental biology connect to darwin
New Evidence: The field of evolutionary developmental biology has revealed that small changes in the timing, location, or expression of genes during development can lead to major changes in an organism’s form. Genes that control development (such as Hox genes) are shared by many organisms and have evolved to produce a diversity of forms.
How It Fits: Shows that evolution can occur by modifying existing developmental pathways, rather than by creating new structures from scratch, which fits with Darwin’s idea of modification of existing traits.
No Inconsistencies: This field reinforces Darwin’s principle of descent with modification by explaining how complex forms can evolve from simpler ancestors through changes in gene regulation.
how does new evidence of direct observations of evolution relate to darwin
New Evidence: Darwin didn’t have direct experimental evidence of evolution happening in real-time, but today, we can observe it. For example, we’ve seen bacteria evolve resistance to antibiotics and finch beaks change size in response to environmental pressures in the Galápagos.
How It Fits: These real-time observations confirm Darwin’s ideas about how natural selection operates. We can directly see evolution in action, such as mutations providing advantages and becoming more common in a population.
No Inconsistencies: These observations provide real-world examples of Darwin’s mechanisms at work.
evidence of evolution in fossils
fossils in younger strata increasingly resemble modern species in same region
-older strata show increasing differences (descent with modification)
homology
similarity of traits in 2 or more species that is due to inheritance from a common ancestor (shared ancestry)
-same structure, different function
vestigial structures
-features inherited from an ancestor, but reduced in morphology and function
-homologous to functional structures in related species
-not required for survival
vestigial traits relating to evolution
provide evidence of the evolutionary past
-have no function (or reduced function) in surviving organisms
-can only be explained by the presence of functional traits in ancestors followed by evolutionary degradation
evidence from biogeography - galapagos
-flora and fauna colonized from mainland South America
-species capable of long-distance dispersal
-distinct forms on different islands provide evidence of early stages of speciation
speciation
one species splits into 2
-factors cause them to become too different to mate = considered diff. species
species vary locally
appearance depends on environ and evolved adaptations
how does australia demonstrate high endemism
has many species found nowhere else in the world
-isolated from other land masses
biogeographically isolated regions
-have species adapted to niches unusual for their group
-harbor endemic radiations of species that are convergent(evolved independently, look similar) with radiations elsewhere
