2024 Chapter 1 Lecture 1.pptm

The Scientific study of Life Chapter 1: Lecture 1 Ms. Thabisa Mdlangu Biodiversity and Conservation Biology Department Life Sciences Building, 5th floor, Core 2 Email: [email protected] Biology: The study of Life What is life? There is no concise definition of life Scientists define life according...

The Scientific study of Life Chapter 1: Lecture 1 Ms. Thabisa Mdlangu Biodiversity and Conservation Biology Department Life Sciences Building, 5th floor, Core 2 Email: [email protected] Biology: The study of Life What is life? There is no concise definition of life Scientists define life according to five qualities (characteristics) that, in combination, constitute life The five characteristics that constitute life 1) Organisation Atoms molecules organelles cells 2) Energy Use Metabolism 3) Maintenance of Internal Consistency Homeostasis 4) Reproduction, Growth and Development Sexual and Asexual Reproduction 5) Evolution Natural Selection tissues organs organ systems…. 1. Life’s organization Hierachy o Atom: The smallest chemical unit of a type of pure substance (element) e.g. Carbon atom o Molecule: A group of joined atoms e.g. DNA o Organelle: A membrane-bounded structure that has a specific function in a cell o Cell: The fundamental unit of life (Unicellular & Multicellular organisms) o Tissue: A collection of specialized cells that function in a coordinated fashion (Epidermis of a leaf) o Organ: A structure consisting of tissues organized to interact and carry out specific functions e.g. Leaf o Organ system: Organs connected physically or chemically that function together o Organism: A single living individual e.g. One acacia tree o Population: a group of the same species of organisms living in the same place and time e.g. multiple acacia trees o Community: Populations of different species that occupies the same region at the same time e.g. all populations in the savanna o Ecosystem: The living and non-living components of the area e.g. the savanna o Biosphere: The global ecosystem, the parts of the planet and its atmosphere where life is possible 2. Life requires energy Inside each cell, countless chemical reactions sustain life. These are collectively called metabolism. They allow organisms to acquire and use energy and nutrients to build new structures, repair old ones and reproduce Organisms are divided into broad categories based on their source of energy o Autotrophs/ Primary producers: make their own food by extracting energy and nutrients from non-living sources o Heterotrophs/ Consumers: Obtain energy and nutrients by eating other organisms, living or dead o Decomposers: Heterotrophs that absorb energy and nutrients from wastes or dead organisms 3. Life maintains constancy The conditions within a cell must remain within a constant range even if the environment surrounding changes The cell must contain a certain temperature, it will die if it becomes too hot or too cold The cell must take in nutrients, excrete waste, and regulate its many chemical reactions to prevent a shortage or surplus of essential substances Homeostasis: The state of internal constancy The cell must maintain homeostasis by counteracting changes as they occur - Organisms must be able to sense and to react to stimuli 4. Life reproduces, grows and develops Organisms reproduce: Make other organisms that are similar to them Reproduction transports DNA from generation to generation Genetic information defines the inherited characteristics of the offspring Reproduction occurs in two basic ways: Asexually: means that the genetic info comes from one parent and all offspring are virtually identical E.g. Bacteria- reproduce asexually by doubling and dividing the contents of the cell Sexual reproduction: Genetic traits from two parents unite and have an offspring , which has a new combination of inherited traits By mixing genes at each generation, sexual reproduction results in tremendous diversity in a population Genetic diversity - enhances the chances that some individuals will survive even if conditions change Sexual reproduction is a very successful strategy especially in an environment where conditions change fervently Sexual reproduction is common among plants, animals and fungi Each organism has to develop into an adult before it can reproduce: must mature 5. Life evolves Life ensures that organisms are well suited for their environment: The teeth of organisms that feed on certain material – like wood are adapted for that type of feeding Adaptation: Tubular flowers have exactly the right shape for the beaks of their hummingbird pollinators Picture source: https://s.hdnux.com/photos/01/32/31/24/23696672 /3/rawImage.jpg Adaptation Predator – Praying mantis (Head, thorax, and forelegs adapted for its sitting and waiting foraging strategy) Source: https://triviaquestionforkids.com/wp-content/uploads/20 21/03/praying-mantis-190189_1280.jpg Adaptation Some organisms have colour patterns that enable them to fade into the background (Camouflage). ‘The Peppered moth is an interesting example of natural selection and behavioral adaptation, If the moth had not been able to adapt its colouration to the humanimpacted environment, it likely would have gone extinct over a century ago. It’s a near miss because human influences almost had serious consequences for this species.’ Source: The Near Miss Moth – BIOL420 @UN BC – Animal Behaviour (opened.ca) An adaptation: is an inherited characteristic or behavior that enables an organism to survive and reproduce successfully in its environment Of all the offspring in a population, the ones that will outcompete the others and live long enough to reproduce are the ones with the best adaptations. The tree of life Taxonomy: The science of branching and classifying organisms Species: The basic unit of classification which designates a distinctive ‘type’ of organism Genus: Closely related species are grouped into the same genus Genus species: Together they denote the unique twoword scientific name of each species Homo sapiens, Musca domestica Glossary of terms Autotrophs/ Primary producers Heterotrophs/ Consumers Decomposers Homeostasis Genetic information Asexual reproduction Sexual reproduction Adaptation Atom Molecule Organelle Cell Tissue Organ Organ system Organism Population Community Ecosystem Biosphere Taxonomy Species Genus