NS 201 Lecture 2.1 - Life on Earth - Biodiversity PDF

NS 201 - Lecture 2.1: Life on Earth – Biodiversity Dr. Jenni Austiff NS201, Team U 11 September 2024 Reminders… Complete week 2 readings 2.2 - Bio 2e: Ch 44.1, 44.2, 44.5, 46.3 2.2 - Trophic Cascades in Salt Marsh Ecosystems (HHMI video) (also recommended for Lab 1B) Complete H...

NS 201 - Lecture 2.1: Life on Earth – Biodiversity Dr. Jenni Austiff NS201, Team U 11 September 2024 Reminders… Complete week 2 readings 2.2 - Bio 2e: Ch 44.1, 44.2, 44.5, 46.3 2.2 - Trophic Cascades in Salt Marsh Ecosystems (HHMI video) (also recommended for Lab 1B) Complete Hall’s Pond Worksheet due before start of your lab period next week Read Lab 1: Part B for next week Fill out get to know you survey Send me accommodations letters ASAP Lecture 2.1 - Outline 1. Origins of Life and Biodiversity 2. History of Classification of Biodiversity 3. Amount and Distribution of Biodiversity 4. Threats to Biodiversity What is Biodiversity? Biodiversity → the number of species and their relative abundance to each other in a given space Biodiversity is a product of evolution Biodiversity Over Time Understanding the ecological context and evolutionary relationships of organism can help us understand the history of life and biodiversity on Earth Humans are a very recent addition to Earth’s biodiversity For most of life’s history, organisms were single celled Origins of Life Early earth (over 4 billion years ago) was… very hot, very little liquid water very little oxygen (anoxic) lacked and ozone layer → radiation exposure Artist depiction of early Earth Earth after a few billion years… The First Organisms Prokaryotes (bacteria) evolved ~3.8 bya small, single-celled Anaerobic (no oxygen) Typical modern prokaryotic cell Oxygen Revolution Cyanobacteria small, single-celled Evolved ability to produce oxygen and transformed Earth’s atmosphere Modern cyanobacteria Cyanobacteria fossil Eukaryote Evolution Eukaryotes evolved have a “true nucleus” and other cell structure called “organelles” organized by membranes Origins of Multicellularity Multicellular organisms can grow larger Ability to specialize cell types Evolved body organization via different cell types Dickinsonia fossil and reconstruction Diversification of Multicellularity Multicellularity evolved several times… Plants Animals Fungi etc. Choanoflagellate, a modern organism – seen as an individual cell and a facultative colony Diversification of Multicellularity Cambrian Explosion was a huge diversification of animals that occurred in the seas (~500 mya) Plants were first to begin diversifying on land Advantages: more light, avoid predation, less competition, access to nutrients (more oxygen). Animals followed plants and further diversified on land Artist depiction of early land plants Artist depiction of Cambrian animals Present Day Biodiversity Plants Fungi Animals Present Day Biodiversity Plants Fungi Animals László Nagy Laboratory Present Day Biodiversity Plants Fungi Animals Classification of Biodiversity Taxonomic diversity → number of species Taxonomy → classification and naming of organisms/species In order to accurately count the number of species and their abundance we also need to know what a species is What is a species? Biological species → group of organisms that can interbreed to produce fertile offspring (other definitions we won’t use) Different species can look the same Members of the same species vary Historical Classification Aristotle’s Ladder of Nature (300s BC) Scala naturae (“Great Chain of Being”) → ranking of beings based on Christian beliefs in middle ages (~1500s AD) Linnaean Classification Carolus Linnaeus (Carl von Linné): developed starting point of modern classification but believed species were fixed Systema Naturae (1735) nested classes of organisms Binomial Nomenclature → two part naming system we use today Ursus americanus Ursus = genus americanus = species Problems with Linnaean Classification But Linnaeus also used his schema on humans in a way that would become the basis of “scientific” racism classified humans based mainly on European cultural prejudices around skin color & geography Scientific racism → the pseudoscientific belief that empirical evidence exists to support or justify racism The concept of human “races” is an unscientific concept with no biological basis continues to be disproven including using newer methods of DNA sequencing and analysis empirical evidence shows that human genetic variation is continuous with no discrete boundaries Tree Thinking Types of organisms within nested system began to be depicted as a tree structure grouped by similarity Phylogenetic tree → visual representation of the similarity/relationships between species originally based only on morphology (i.e. physical characteristics), later genetics was not originally about evolutionary relationships Biodiversity is a Product of Evolution Phylogenetic trees can be organized to reflect a hypothesis about the evolutionary history and relationships of organisms/groups All of Earth’s biodiversity can be represented on a phylogeny Evolutionary Principles Trees can represent different sub-groups of interest can represent different sub-groups of interest Branches can represent single species (i.e. taxon) or groups of organisms (i.e. clade) Sister groups → next to each other on the tree and are more closely related to each other than other groups Common ancestors → extinct organisms that groups evolved from in the evolutionary past and are represented on the nodes where branches split Molecular Phylogeny Knowledge of DNA and the invention of DNA sequencing also allows us to compare molecular data Prior to molecular evidence, live was divided into “5 Kingdoms” DNA evidence restructured our classification of life into 3 Domains: Bacteria, Archaea, Eukarya (Woese, et al., 1990) Measuring Biodiversity Biodiversity → the number of species and their relative abundance to each other in a given space Species richness → number of species in a location Relative abundance → how many of each type of species is present in relationship to the other species Which example is more species rich? Which is more diverse? Distribution of Biodiversity Why do some areas have more species? Map of amphibian species across the globe Distribution of Biodiversity Why do some areas have more species? Latitude (north-south): higher primary energy input from the sun closer to the equator and more stable climate Age of ecosystem - temperate ecosystems are “younger” because of last ice age (but don’t forget sampling bias! – some areas are understudied) Biodiversity Hotspots Biodiversity hotspots → geographical areas that contain high numbers of endemic species - important to conserve! Endemic Species Native species → occur in a certain ecosystem due to natural distribution and natural evolution Endemic species → native to a single geographical location - i.e. evolved in one location and never spread out Example: Madagascar is an island that separated from India ~88 mya. Thousands of endemic species, 5% of all known species on Earth There are approximately 150 species of chameleons, 110 species of lemurs, and over 1000 species of orchids on Madagascar. Amount of Biodiversity 2.13 million species described and counting… (counts via IUCN Red List, 2022) Most things are invertebrates! Most invertebrates are insects! Non-insect invertebrates > all vertebrates (Microorganisms not included) Estimating Biodiversity Predictions by Mora, et al. (2011) These numbers are likely underestimates… What are some reasons for debate over the number of species estimates? Discovering New Species Are new species still being discovered? Yes! - predicted millions more to describe some are known by people who have lived alongside them for many thousands of years but are new to being “described” scientifically Race to describe new species before they go extinct! Species Extinction Extinction → a species entirely dies out functionally extinct: population become so small it cannot recover The number of species on Earth is dependent on the rates of speciation and extinction There is typically a background level of speciation and extinction (i.e. what is normal) Yangtze giant softshell turtle only has 3 surviving individuals Thylacine - extinct marsupial dog Mass Extinction Mass extinction → sudden, dramatic loss of biodiversity (>½ of species alive at that time) Endangered Species IUCN Red List tracks endangered species (website) 6th Mass Extinction?? At the beginnings of what could be 6th mass extinction event Human driven → likely began with European global colonization Habitat loss & fragmentation Overharvesting Species introductions Pollution Climate change Habitat Loss Map of old growth forests in the United States Loss of prairie habitats due to farmland in central United States Invasive Species Biological “colonization” → species spread to new areas naturally Introduced species (non-native) → living outside of its native/historical distribution range, relocated by director or indirect human activity Some cannot survive and are not a problem, or otherwise do not negatively impact the ecosystem Invasive species → survive and harm the native species and disrupt the ecosystem adaptive mismatch between species and new ecosystem because they evolved in a different original ecosystem Cane Toads in Australia Conservation of Biodiversity Changing human behavior restrictions through legislation individual/community values Sustainability → reduce and radically alter human consumption patterns Habitat restoration and nature preserves with wildlife corridors Captive breeding of endangered species Climate change mitigation → reduce use of fossil fuels, either through clean technologies or lowering energy use overall Habitat Restoration Habitat restoration → rehabilitation the degradation, damage or destruction already done of an area to recreate a functioning ecosystem, and recover what was lost traditionally measured in species richness newer metrics also consider genetic diversity, species interactions, and ecological networks can take centuries to fully recover but some loss cannot be restored - evolution takes thousands and millions of years! It is more effective to preserve intact habitats Invasive Species Management Prevention → monitoring, inspection, and quarantine Removal and elimination of invasive species Value of Biodiversity Reminders… Complete week 2 readings 2.2 - Bio 2e: Ch 44.1, 44.2, 44.5, 46.3 2.2 - Trophic Cascades in Salt Marsh Ecosystems (HHMI video) (also recommended for Lab 1B) Complete Hall’s Pond Worksheet due before start of your lab period next week Read Lab 1: Part B for next week Fill out get to know you survey Send me accommodations letters ASAP