Millions of years ago no flowers existed. The entire world was green. Then, about 300 million years ago something amazing happened. Plants began changing the way they reproduced. As a result the distant ancestors of modern flowers were born. These plants did not yet have pollen, nectar, fragrance, brilliant colors, or even large blooms.
Gymnosperms, the plants that existed before flowers, reproduced from spores rather than seeds. The earliest flowering plants reproduced from seeds and are believed to be aquatic plants. Some evidence exists that suggests water lilies were among the earliest flowering plants.
The evolutionary progress of ancient flowers was slow at first. About 125 million years ago however, they began evolving and diversifying rapidly. This diversification occurred together with pollinating insects. In fact, much of what we currently know of these flowers, we learned by studying the pollinating insects of the period. Scientists don’t yet know what triggered the rapid development.
Within 50 million years angiosperms became the most diverse species of plants as well as the dominant type of plant on earth. Co-evolution with insects eventually led flowers to develop bright colors, attractive patterns, and fragrant aromas to attract insects and other pollinators. The co-evolution with insects also led to changes in how the flowers were pollinated. The physical structures of the plants became more diverse to attract a wider range of pollinators.
Evidence of this evolution is extremely scarce. As a result scientists have more theories than proof. The evidence that does exist consists of fossils and amber. Amber is hardened golden resin exuded by some trees. Insects or plant material caught within the resin are preserved in remarkable three dimensional detail. Bees encapsulated in amber are often coated in pollen that can be identified as coming from a specific plant species.
Flowers have changed radically since their emergence millions of years ago. In some small but important ways, flowers have changed the world we know today. We have much to learn about prehistoric flowers, but the evidence left in both fossils and amber gives us a tantalizing glimpse of an ancient world very beautiful and very different from our own.
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* Hank talks about population genetics, which helps to explain the evolution of populations over time by combing the principles of Mendel and Darwin, and by means of the Hardy-Weinberg equation.
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Table of Contents:
1. Population Genetics 1:05
2. Population 1:14
3. Allele Frequency 1:41
4. 5 Factors 1:58
a) Natural Selection 2:12
b) Natural Selection/Random Mating 2:27
c) Mutation 3:18
d) Genetic Drift 3:49
e) Gene Flow 4:05
5. Hardy-Weinberg Principle 4:45
6. Hardy-Weinberg Equilibrium 5:15
7. Hardy-Weinberg Equation 6:18
gregor mendel, heredity, genetics, charles darwin, natural selection, evolution, offspring, population genetics, species, population, generation, allele frequency, allele, selective pressure, sexual selection, non-random mating, preferred traits, fitness, mutation, DNA, genetic drift, chance, gene flow, immigration, emigration, godfrey hardy, wilhelm weinberg, hardy-weinberg equation, hardy-weinberg equilibrium, phenotype, genotype, earwax, mendelian trait, homozygous, heterozygous, evolutionary biology
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Population Genetics: When Darwin Met Mendel – Crash Course Biology #18