A4 Unity and diversity: Ecosystems Flashcards
How do DNA/RNA and amino acid sequences provide evidence for evolution?
Species that share a more recent common ancestor have fewer differences in base or amino acid sequences.
Molecular similarities suggest evolutionary relationships and the accumulation of mutations over time.
How does selective breeding support evidence for evolution?
Humans have artificially selected traits in animals and crops over generations, leading to heritable changes in phenotypes.
This mimics natural selection and shows how descent with modification occurs.
(E.g. dogs from wolves, cabbages from wild mustard. It’s evolution on fast-forward.)
What are homologous structures, and how do they support evolution?
Homologous structures have the same basic structure but different functions, suggesting a common ancestor.
E.g. forelimbs of humans, bats, and whales.
What is convergent evolution, and what are analogous structures?
Convergent evolution occurs when unrelated species develop similar features due to similar selective pressures.
Analogous structures look/function alike but evolved independently, e.g. wings of birds and insects.
What’s the difference between sympatric and allopatric speciation?
Allopatric: populations are physically separated (e.g. by mountains or rivers)
Sympatric: populations live in the same area but diverge through behavioral or genetic isolation
What is adaptive radiation, and why does it matter?
When a single species rapidly evolves into multiple new species to fill different niches.
Often follows isolation or new habitats, e.g. Darwin’s finches.
How do hybrid sterility and reproductive barriers prevent allele mixing?
Prezygotic barriers: mating doesn’t happen (e.g. different mating times)
Postzygotic barriers: hybrids form but are sterile or inviable
These prevent gene flow and maintain species boundaries.
How does polyploidy cause speciation in plants?
A polyploid plant has more than two sets of chromosomes, often due to errors in meiosis.
If it can’t reproduce with parent species, it becomes reproductively isolated, causing instant speciation.
How does today’s species count compare to past biodiversity?
Earth has millions of species today, but mass extinctions and speciation events have caused fluctuations.
Current rates of extinction are higher than historical averages, raising concern.
Why do we need multiple conservation strategies?
Different species and ecosystems face different threats.
Using in-situ (Protecting species in their natural habitats), ex-situ (Protecting species outside their natural habitats), legal (Laws and policies to protect species and ecosystems), and community-based methods (Involves local communities in conservation efforts) increases success.
What is the EDGE of Existence program, and why is it important?
It focuses on species that are both evolutionarily unique and globally endangered.
These species are irreplaceable—losing them means losing an entire branch of the evolutionary tree.
