La biodiversité et son évolution - Term enseignement scientifique - Madame SVT

Did you like this video? Will it help you get a good grade on your next test? Leave me a like and subscribe so I know 😊 To support my work, you can leave a little tip here ➡️ https://fr.tipeee.com/madame-svt I AM: ON INSTAGRAM: @madame.svt -   / madame.svt   ON FACEBOOK "Madame SVT" -   / madame.svt   AND ON TIKTOK: https://vm.tiktok.com/ZMd7Ukf1S/ Link to the revision sheet to download ➡️ https://drive.google.com/file/d/1n9Mw... The chapter "Biodiversity and its "Evolution" is part of Theme 3 "A History of Life" in the final year of science curriculum. Knowledge and skills developed in this chapter, according to the official bulletin (official curriculum) 📖: Assessing biodiversity at different spatial and temporal scales is a major challenge for understanding its dynamics and the consequences of human actions. Populations evolve over time. Probabilistic mathematical models and statistical tools allow us to study the evolutionary mechanisms involved. There are a large number of species on Earth, of which only a small proportion are actually known. Biodiversity is measured using sampling techniques (species or DNA) that allow us to estimate the number of species (species richness) in different environments. The components of biodiversity can also be described by the abundance (number of individuals) of a population, a species, or a larger taxon. There are several methods for estimating a population size from samples. The capture-mark-recapture method is based on calculations performed on a sample. If we assume that the proportion of marked individuals is identical in the recapture sample and in the total population, the population size is obtained by calculating a proportional fourth. From a single sample, the population size can also be estimated using a confidence interval. Such an estimate is always accompanied by a confidence level strictly less than 100% due to sample fluctuation. For a given confidence level, the larger the sample size, the more precise the estimate becomes. During biological evolution, the genetic composition of a species' population changes from generation to generation. The Hardy-Weinberg mathematical model uses probability theory to describe the random phenomenon of allele transmission in a population. By equating probabilities with frequencies for large population sizes (law of large numbers), the model predicts that the genetic structure of a large population is stable from one generation to the next under certain conditions (absence of migration, mutation, and selection). This theoretical stability is known as Hardy-Weinberg equilibrium. The discrepancies between the frequencies observed in a natural population and the model's results can be explained in particular by the effects of evolutionary forces (mutation, selection, drift, etc.). Human activities (pollution, destruction of ecosystems, eruption and its climatic impacts, overexploitation of species, etc.) have consequences on biodiversity and its components (including variations in abundance) and lead to the extinction of species. The fragmentation of a population into several samples of smaller numbers leads to a reduction in the genetic diversity of a population through genetic drift. Understanding and managing an ecosystem helps preserve its biodiversity. Happy revision! 😉 Creation music: "Atlantis" by Scandinavianz (   • Atlantis – Scandinavianz (No Copyright Music)  )