Studying Life

1. Studying Life

2. 1 Studying Life • 1.1 What Is Biology? • 1.2 How Do Biologists Investigate Life? • 1.3 Why Does Biology Matter?

3. 1 Studying Life • More than one-third of the world’s amphibian species are threatened with extinction. • Tyrone Hayes studies one of the threats to amphibians—agricultural pesticides such as atrazine, which impact breeding and reproduction. Opening Question: Could atrazine in the environment affect species other than amphibians?

4. 1.1 What Is Biology? • Biology is the scientific study of living things (organisms). • Living things are all descended from a common origin of life that occurred almost 4 billion years ago.

5. Figure 1.1 The Many Faces of Life (Part 1)

6. Figure 1.1 The Many Faces of Life (Part 2)

7. 1.1 What Is Biology? • Characteristics of living organisms: • Made of a common set of chemical components: carbohydrates, fatty acids, nucleic acids, amino acids • Most are made of cells enclosed by plasma membranes • Convert molecules from their environment into new biological molecules

8. 1.1 What Is Biology? • Extract energy from the environment and use it to do biological work • Contain genetic information that uses a universal code to specify proteins • Share similarities among a fundamental set of genes, and replicate this genetic information when reproducing

9. 1.1 What Is Biology? • Exist in populations that evolve through changes in frequencies of genetic variants over time • Self-regulate their internal environment, maintaining conditions that allow them to survive

10. 1.1 What Is Biology? • The diverse organisms alive today all originated from one life form. • If life had multiple origins, we would not expect to see such striking similarities in gene sequences, genetic code, and amino acids.

11. 1.1 What Is Biology? • Earth formed 4.6 to 4.5 billion years ago but it was 600 million years or more before life evolved. • The history of Earth can be pictured as a 30-day month.

12. Figure 1.2 Life’s Timeline

13. 1.1 What Is Biology? • Complex biological molecules probably arose through random physical associations of chemicals. • Experiments simulating conditions on early Earth show that this is possible, and even probable.

14. 1.1 What Is Biology? • Nucleic acids were essential— molecules that could reproduce themselves and serve as templates for synthesis of proteins. • Another step was enclosure of biological molecules by membranes. This created an internal environment in which reactions could be controlled and integrated.

15. Figure 1.3 Cells Are Building Blocks for Life

16. 1.1 What Is Biology? • For 2 billion years, life consisted of single cells called prokaryotes. • The two main groups of prokaryotes emerged early: bacteria and archaea.

17. 1.1 What Is Biology? • Some early prokaryotes began to live in close, interdependent relationships and eventually merged to form a third major lineage of life, the eukaryotes. • Eukaryotic cells have internal membranes that enclose specialized organelles within their cells, including the nucleus, which contains the genetic material.

18. 1.1 What Is Biology? • At some point, eukaryotic cells did not separate after division and started living as colonies. • This opened the way for some cells to specialize for certain functions, which led to multicellular organisms.

19. 1.1 What Is Biology? • About 2.5 billion years ago, photosynthesis changed the nature of life on Earth. • This process transforms sunlight energy into biological energy. • Photosynthesis is the basis of most of life on Earth; it provides food for other organisms.

20. 1.1 What Is Biology? • Early photosynthetic cells were probably similar to cyanobacteria(prokaryotes). • The atmosphere of early Earth had no O2, but it began to increase as photosynthetic prokaryotes increased. • Organisms that could tolerate O2 proliferated.

21. Figure 1.4 Photosynthetic Organisms Changed Earth’s Atmosphere

22. 1.1 What Is Biology? • Abundant O2 opened up new avenues of evolution because aerobic metabolism is more efficient than anaerobic metabolism and allows organisms to grow larger.

23. 1.1 What Is Biology? • O2 in the atmosphere also allowed life to move onto land. • Accumulating O2 led to formation of the ozone (O3) layer, which absorbs damaging UV radiation. • By 500 million years ago, there was enough ozone for organisms to leave the protection of the water.

24. 1.1 What Is Biology? • Genome: the sum total of all the DNA in a cell. • DNA consists of repeating subunits called nucleotides. • Gene: a specific segment of DNA that contains information for making a protein.

25. Figure 1.5 DNA Is Life’s Blueprint

26. 1.1 What Is Biology? • All the cells of a multicellular organism have the same genome, yet different cells have different functions and structures. • Different cells are expressing different parts of the genome.

27. 1.1 What Is Biology? • The genome must be replicated when cells reproduce. • The process is not perfect; errors are called mutations. • Discovery of DNA and how it functions transformed biological science.

28. 1.1 What Is Biology? • A population is a group of individuals of the same type of organism—the same species—that interact with one another. • Evolution acts on populations; it is change in the genetic makeup of populations through time.

29. 1.1 What Is Biology? • Evolution is the major unifying principle of biology. • Charles Darwin compiled factual evidence for evolution. • He argued that differential survival and reproduction among individuals in a population (natural selection) could account for much of the evolution of life.

30. 1.1 What Is Biology? • Darwin proposed that all organisms are descended from a common ancestor. • Some mutations give rise to changes in organisms; genetic variants may change in frequency in the population —the population evolves.

31. 1.1 What Is Biology? • Darwin knew that humans select for specific traits in domesticated animals (artificial selection); the same process could operate in nature (natural selection). • Only a small percentage of an individual’s offspring survive to reproduce; thus traits that confer an increase in the probability of survival and reproduction will spread in the population.

32. 1.1 What Is Biology? • Natural selection leads to adaptations: structural, physiological, or behavioral traits that enhance an organism’s chances of survival and reproduction.

33. Figure 1.6 Adaptations to the Environment

34. 1.1 What Is Biology? • As populations become isolated and evolve differences, they are eventually considered different species. • Species that share a recent evolutionary history are generally more similar to each other than species that share a more distant ancestor.

35. 1.1 What Is Biology? • Each species has a distinct scientific name, a binomial: • Genus name – species name • Example: Homo sapiens • A genus is a group of species that share a recent common ancestor.

36. 1.1 What Is Biology? • Our understanding of evolutionary relationships has been greatly enhanced by molecular techniques such as the ability to sequence genomes. • A phylogenetic tree illustrates the evolutionary histories of different groups of organisms.

37. Figure 1.7 The Tree of Life

38. 1.1 What Is Biology? • Three domains of life: • Bacteria (prokaryotes) • Archaea (prokaryotes) • Eukarya(eukaryotes)

39. 1.1 What Is Biology? • For more than half of Earth’s history, all life was unicellular. Unicellular species remain ubiquitous and highly successful in the present. • Multicellular Eukarya (plants, animals, and fungi) evolved from protists—unicellular microbial eukaryotes.

40. 1.1 What Is Biology? • Cells became specialized in multicellular organisms; a biological hierarchy emerged: • Differentiated cells are organized into tissues. Different tissue types form organs (e.g., a heart); and organs are grouped into organ systems.

41. Figure 1.8 Biology Is Studied at Many Levels of Organization (1)

42. 1.1 What Is Biology? • A group of individuals of the same species is a population. • Populations of all the species that live and interact in a defined area are called a community. • Communities together with their abiotic (nonliving) environment constitute an ecosystem.

43. Figure 1.8 Biology Is Studied at Many Levels of Organization (2)

44. 1.1 What Is Biology? • Individuals may compete with each other for resources; • Or they may cooperate (e.g., in a termite colony). • Plants also compete for light and water, and many form complex partnerships with fungi, bacteria, and animals.

45. 1.1 What Is Biology? • The interactions of plant and animal species are major evolutionary forces that produce specialized adaptations. • Species interactions with one another and with their environment is the subject of ecology.

46. 1.1 What Is Biology? • Organisms acquire nutrients from their environment. • Nutrients supply energy and materials for biochemical reactions. • Some reactions break nutrient molecules into smaller units, releasing energy for work.

47. 1.1 What Is Biology? • Examples of cellular work: • Movement of molecules or the whole organism • Synthesis—building new complex molecules from smaller chemical units • Electrical work of information processing in nervous systems

48. Figure 1.9 Energy Can Be Used Immediately or Stored

49. 1.1 What Is Biology? • Organisms must regulate their internal environment, made up of extracellular fluids. • Maintenance of the narrow range of conditions that support survival is known as homeostasis.

50. 1.2 How Do Biologists Investigate Life? • Scientific investigations are based on observation, data, experimentation, and logic. • Observation has been improved by new technologies. • Information, or data, must be quantified using mathematical and statistical methods.