When first proposed, Darwin's theory of natural selection did not fully explain how evolution could occur. This was due to _________.
Darwin's theory of natural selection, introduced in "On the Origin of Species" (1859), proposed that species evolve over time through the process of natural selection, where individuals with advantageous traits are more likely to survive and reproduce. However, when first proposed, the theory faced a significant gap: it did not fully explain how variations are inherited or how they arise in populations. This was primarily because the mechanisms of genetic inheritance were not yet understood or widely known.
Step 1: Understand Darwin's Theory
Darwin observed that: But he lacked a clear mechanism for how traits are passed from parents to offspring.
Step 2: Identify the Missing Piece
At the time, genetics was not established. Gregor Mendel's work on inheritance (1865) was not recognized until later. Without knowledge of genes, alleles, or DNA, Darwin could not explain how variations were inherited or how new variations appeared.
Step 3: Evaluate the Options
- Darwin did recognize over-reproduction (it's a key part of his theory), so options 1 and 3 are incorrect.
- Embryological descriptions were not the core issue; inheritance was.
- The correct reason is that accurate mechanisms for genetic inheritance were not widely known.
Final Answer: The fact that accurate mechanisms explaining genetic inheritance were not widely known.
1. Natural Selection: Process where organisms better adapted to their environment tend to survive and produce more offspring. Formula for fitness:
2. Mendelian Genetics: Explains inheritance through genes. For a trait with two alleles (A dominant, a recessive), offspring genotype ratios follow:
3. Modern Synthesis: Combines Darwin's natural selection with Mendelian genetics, explaining evolution through changes in allele frequencies over time, calculated using the Hardy-Weinberg principle: where is frequency of dominant allele, is frequency of recessive allele.
Darwin's theory of natural selection, introduced in "On the Origin of Species" (1859), proposed that species evolve over time through the process of natural selection, where individuals with advantageous traits are more likely to survive and reproduce. However, when first proposed, the theory faced a significant gap: it did not fully explain how variations are inherited or how they arise in populations. This was primarily because the mechanisms of genetic inheritance were not yet understood or widely known.
Step 1: Understand Darwin's Theory
Darwin observed that: But he lacked a clear mechanism for how traits are passed from parents to offspring.
Step 2: Identify the Missing Piece
At the time, genetics was not established. Gregor Mendel's work on inheritance (1865) was not recognized until later. Without knowledge of genes, alleles, or DNA, Darwin could not explain how variations were inherited or how new variations appeared.
Step 3: Evaluate the Options
- Darwin did recognize over-reproduction (it's a key part of his theory), so options 1 and 3 are incorrect.
- Embryological descriptions were not the core issue; inheritance was.
- The correct reason is that accurate mechanisms for genetic inheritance were not widely known.
Final Answer: The fact that accurate mechanisms explaining genetic inheritance were not widely known.
1. Natural Selection: Process where organisms better adapted to their environment tend to survive and produce more offspring. Formula for fitness:
2. Mendelian Genetics: Explains inheritance through genes. For a trait with two alleles (A dominant, a recessive), offspring genotype ratios follow:
3. Modern Synthesis: Combines Darwin's natural selection with Mendelian genetics, explaining evolution through changes in allele frequencies over time, calculated using the Hardy-Weinberg principle: where is frequency of dominant allele, is frequency of recessive allele.